SU864487A1 - Method of regulating load current of power-diode electric drive - Google Patents

Description

(54) METHOD FOR REGULATING THE VOLTAGE ELECTRIC DRIVE LOAD CURRENT The invention relates to electrical engineering, in particular to electric drives with valve converters. A known method of regulating the load current of a valve electric drive, which consists in generating a current reference signal and a sweep signal synchronized with the mains voltage, measures the instantaneous value of the load current and opens the next one. The converter gate at the moment of equality of two compared signals, one of which is a sweep signal. The signal with which the sweep signal is compared is formed from the difference between the two signals — a current setting signal and a signal proportional to the instantaneous value of the load current. The sweep signal is generated as a periodic function, the shape of which in each period is unchanged by til. The disadvantage of the method is the dependence of the system speed on the magnitude of the reference signal. The closest to the invention in its technical nature is a method for controlling the load current of a valve electric drive, in which a reference signal proportional to a predetermined average value of the load current synchronized with the supply network of the sweep signal is measured, the instantaneous load current is measured, two signals are compared, one of which is the sweep signal, and, according to the latter’s elevation, pulse control signals are generated by the Converter electric drive. In this method, the sweep signal is compared with the reference signal, which determines the maximum current value, which allows to provide speed-limiting processes in a certain range of opening angles of the converter valves, the duration of which is equal to one conduction interval of the converter transformer G21 The disadvantages of this method are the inaccuracy of current average control load and reduced speed, which takes place at the angles of regulation, differ from 90, because of the regulated the maximum value of the current. The purpose of the invention is to improve the accuracy of regulation while ensuring speed-limiting processes.

This goal is achieved in that the method additionally measures the motor's EMF, summarizes the reference signal and a signal proportional to the motor's EMF, converts the sum signal into a sweep signal corresponding to a given instantaneous load current, and as the signal with which the scan signal is compared, signal proportional to the measured instantaneous value of the load current.

FIG. 1 shows a block diagram of one embodiment of a device implementing the method, and FIG. 2 time diagrams for his work.

The device contains a valve converter 1, the power supply 2 of a DC motor, a load current sensor 3 and a motor EMF sensor 4. The control electrodes of the converter valves are connected to the output of the pulse former of the pulse distributor 5. The driver / distributor 5 has two inputs. One of the inputs is connected to the network supplying the converter 1, and the second is connected to the output of the zero-organ 6. The input of the zero-organ 6 is connected to the output of the comparison element 7. The negative input element 7 is connected to the output of the current sensor 3. The positive input of the element 7 is connected to the output of the comparison element 8. The positive input of the element 8 is given a signal U y proportional to the average value of a given load current. The negative input element 8 is connected to the output of the functional unit 9, which has two inputs. One input of block 9 is connected to the output of summing element 10, and the other input is connected to the output of the generator 11 of the reference voltage. One input of the summing element 10 is connected to the output of the EMF sensor 4, and the second has a reference signal U. The generator 11 of the reference voltage has two inputs, one of which is connected to the output of the driver-distributor

5, and the second - With the network that supplies the transducer 1.

The device works as follows.

The control pulses on the gates of the converter 1 arrive at the moments when the sweep signal Up becomes larger than the signal U- from the output of the current sensor 3. These moments are detected by the actuation of the zero-body.

6, from the output of which the trigger signal goes to the driver-distributor 5. The latter forms

at the moments of actuation of the zero-organ 6, the control pulses and directs them to the control electrodes of the corresponding gates of the converter 1. The scan signal Up is formed as the difference of the reference signal of the auxiliary signal Ug. A reference signal is generated as a signal proportional to the average value of a given load current in accordance with the expression

and.

R

    The auxiliary signal is formed by block 9 of two signals: a signal representing the difference between the reference signal and a signal proportional to the motor emf} of the reference signal proportional to the current time t read from the natural value of the valve, which enters into operation at the end of the given conduction interval of the converter. The auxiliary signal is defined by the expression

 0 -E -4-i., - cosM cosClDt

and

AT

about -ClJto-t t / LUTfl

1G pack

. Ji: -and) vn TG

g y gsre / mlOTfl

s r {cLo- f} l.

X sin

m I RiH-E spz1 .. arccos

de

Jl

m

Sin

and M-rt

m

tp arctg ji) f,

where I is the current value proportional to the average value of the specified load current, Aj

TD - Electromagnetic Constant

J.

engine, with;

R. - the total active resistance of the core chain, Ohm;

and is the voltage value proportional to the amplitude value, or the phase voltage value of the supply mains at zero, rectification circuits, or linear values at bridge circuits, Bj E is a signal proportional to

The EMF of the engine, Bf t is the current time, measured from the moment of natural ignition of the valve, which is to enter into operation at a given interval of change of the scanning signal, s;

w - the angular frequency of the power se-.

ti, rad / s, m is the pulse impulse of the converter. The controversial signal is generated by the generator 11. in the form of a piecewise continuous signal (Fig 2). The auxiliary signal Ug, as well as the reference signal, is a piecewise continuous signal. As a reference signal and a signal sweep Up must not be less than zero. The sweep signal is defined only there, de signal

the reference is different from zero. The diagrams (Fig. 2) demonstrate the change in the signals of the device under consideration in the course of the reaction to an abrupt decrease in the driving signal.

Claims (2)

value of value} y2. The diagrams are constructed for the case of a three-phase zero converter rectifier circuit. There are also diagrams of phase (UA, Up, U) and output (Uj) transducer voltages excluding the motor EMF. Moments of opening of the converter valves. are t-j + tj. Time intervals are t, etc. . conduction intervals of the converter. The time instant to corresponds to the instant of change of the reference signal. Angle of valve control in moments. t corresponds to the steady state mode of operation with the task Uflf 4 Intermittent change of U-i in tp, leads to intermittent moment. p - .. „. change up. Thanks to the proposed signal sweep form, the pulse at the end of the interval. t, t will be served with such an angle that in the following moments t2, t, etc. steering angle. : will correspond to the established operating mode. Thus, the control method allows to increase the productivity of technological units by improving the accuracy and speed of adjustment. Claims The method of controlling the load current of a valve electric drive, which generates a reference signal, is proportional to the critical average load current, synchronized with the sweep signal, measures the instantaneous value of the load current, compares two signals, one of which is a convolution signal , and, by exceeding the latter, form pulse signals for controlling the converter of the valve electric drive, characterized in that, in order to increase the control accuracy, An electric motor emf is measured, the reference signal and a signal proportional to the motor emf are summed, the total signal is converted into a sweep signal corresponding to a given instantaneous load current, and the signal proportional to the measured instantaneous value is used as a signal with which the scan signal is compared. current nah-ruzki. Sources of information taken into account during the examination 1. USSR author's certificate 540338, cl. H 02 R 13/16, 1976. 2. The patent of Germany No. 2202871, cl. H 02 R 13/16, 1978.