SU1651347A1 - Device for controlling a direct frequency converter with an implicit link - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to improve the shape of the output voltage curve of the frequency converter. A device containing serially connected first adjustable voltage source, frequency reference, recalculating pulse shaper, ring distributor, sawtooth shaper, output shaper, input voltage sensor and second adjustable voltage source, is equipped with an amplifier with adjustable transmission coefficient and comparator The introduction of new units and their connections allows to compensate for the ripple of the supply voltage in an implicit DC link, and thereby improve the shape of the output voltage of the frequency converter. 1 silt (L

Description

The invention relates to electrical engineering and can be used in the construction of direct frequency converters, for example, for frequency control of electric drives and for autonomous power supply systems.

The aim of the invention is to improve the shape of the output voltage curve of the frequency converter.

The drawing shows a diagram of a device for controlling a direct frequency converter with a non-direct DC link.

A device for controlling a direct frequency converter includes an adjustable voltage source 1, the output of which is connected to the input 2 of the setting frequency 3, the driver 4 pulses

recalculation of the input of which is connected to the output 5 of the frequency adjuster 3, the ring distributor 6 to the input of which the output 7 of the driver 4 is connected. Six outputs 8-13 of the distributor are connected respectively to the inputs of the driver 14 of the output signals. The output of the variable voltage source 15 is connected to the input 16 of the amplifier 17 with an adjustable transmission coefficient, the output 18 of which is connected to one input of the comparator 19. The output 20 of the saw 21 of the sawtooth voltage is connected to the other input of the comparator 19 and the output 22 of the comparator 19 is connected to one of shaper inputs 14 To inputs 23-25 of sensor 26 of input voltages three phases of mains supply are connected outputs 27-32 of sensor 26 come together

SP

“A

O) 4

yen with shaper inputs 14 output signals. Inputs 33-35 of the three-phase bridge rectifier 36 are connected to the three phases of the mains supply, and output 37 is connected to the input 38 of the amplifier 17. Outputs 39-47 of the driver 14 are used to control the keys of the frequency converter.

The frequency control key pulses are generated as follows:

The setting device 3, controlled by the voltage of the adjustable source 1, generates a sawtooth signal, whose frequency is six times higher than the frequency of the output voltage of the frequency converter. This signal from the output 5 of the setting device 3 enters the input of the imaging unit 4, the output of which is a sequence of short pulses, corresponding to the front of the setpoint signal. These pulses are fed to the input of the distributor 6, at six outlets 8-13 of which six sequences of rectangular pulses with a duration of 300 e.h. with a frequency six times lower frequency setting 3. The outputs 8-13 of the distributor 6 are connected to the inputs of the imaging unit 14.

The signal for setting the duration of the key control pulses of the frequency converter comes from the source 15 to the input 16 of the amplifier 17. The transfer ratio of the amplifier 17 is controlled by the incoming voltage 38 to the input Uynp., Which is pulsed rectified voltage at the output 37 of the three-phase bridge rectifier 36. The voltage at the output 18 of the amplifier 17 is determined by the formula

11out Ku 1 + cos (g-) - cos (wt -) - DI,

About an |,

where UBX is the voltage of the variable voltage source 15 (input 16 amplifier 17);

Km - scaling factor;

(O- circular frequency of the mains.

Shaper 21 is an autonomous sawtooth generator, the frequency of which is several times higher than the setting frequency 3. As the frequency of the shaper 21 increases, the accuracy of tracking the pulsating voltage of the three-phase rectifier 36 increases, but the limiting factor in this case is dynamic losses in keys direct frequency converter.

A sawtooth signal from the output 20 of the imaging unit 21 is fed to the first input of the comparator 19, to the second input of which

voltage is supplied from the output 18 of the amplifier 17 with an adjustable transmission coefficient for comparison. At the output of the comparator, rectangular pulses are formed, the duration of which varies with the signal from the output of the amplifier 17.

The voltages of the three-phase supply network Da, UB, Uc are fed to the inputs 23-25 of the sensor 26 of the input voltages. From sensor outputs 27-32, six sequences of rectangular pulses are fed to the shaper inputs of the output signals.

The output driver 14 is a combinational logic circuit, the inputs of which receive six signals from the outputs of the distributor 6, the output signal of the comparator 19 and six signals from the outputs of the sensor 26. The driver 14 implements the logic functions

X1 R1-Y1 -RJ-Y6;

X2 R2 -Y1 4-R2-Y6;

X3 R3 -YH-F & - Y6;

X4 R1 -Y2 + -Y5; X5 R2 Y2 + R2 Y5;

X6 R3 -Y2 + R3- Y5;

X7 R1 Y3 R1- Y4;

X8 R2 Y3 R2 Y4

X9 R3 Y3 rfleR1 Z1 + Z2 -Q + Z3 + Z5 -Q;

R2 Z3 + Z4 + Z5 + Z | Q;

R3 Z5 + Z6 -Q + Z1 + Z3 -Q;

Z1-Z6 - signals at the outputs of the distributor;

Y1-Y6 - signals at the outputs of the sensor input voltages;

Q is the signal at the comparator output;

X1-X9 - output signals of the device.

Claims (1)

The proposed device for controlling a direct frequency converter with a non-direct DC link allows to compensate for the ripple of the mains supply voltage in a non-direct DC link, to improve the current harmonic coefficient and the shape of the output voltage of the frequency converter, to reduce losses during operation of the transducer on the active-inductive and motor load. Invention Formula A device for controlling a direct frequency converter with a non-direct DC link, comprising a series-connected first source of adjustable voltage, a frequency reference, a driver of recalculation pulses and a ring distributor, a second adjustable voltage source, a saw driver, a comparator, the first input of which is connected to the output of the sawtooth generator, a logic sensor of the input voltages, the inputs of which are used to connect to the phase the networks, the outputs of the ring distributor, the logic sensor of the input voltages and the comparator are connected to the inputs of the output driver, which implements the logic functions X1 R1 Y1 + R1-Y6, X2 R2 Y1 + R2 Y6, X3 R3 Y1 + R3 Y6, X4 R1 Y2 + Rl Y5, X5 R2 -Y2 + R2 -Y5, X6 R3 Y2 + R3 Y5, X7 R1 Y3 + RJ -Y4, X8 R2 Y3 + R2 Y4. X9 R3- Y3 + R3- Y4,  + Z3 + 75 -Q; Q + Z5 + Z1 -Q; Q + Z1 + Z3-Q; where R1 Z1 + Z2 R2 Z3 + Z4 R3 Z5 + Z6 Z1-Z6 - signals at the outputs of the ring distributor; Y1-Y6 - signals at the outputs of the logic sensor of input voltages; Q is the signal at the comparator output; X1-X9 are the output signals of the driver, the outputs of which are used as outputs of the device; characterized in that in order to improve the shape of the output voltage curve of the frequency converter, it is equipped with an amplifier with an adjustable gain and a three-phase bridge rectifier, with the inputs of the three-phase bridge rectifier connected to the inputs of the logic sensor input voltages, output - to the control input of the amplifier with an adjustable transmission coefficient, the input of which is connected to the output of the second source of adjustable voltage, and the output connected to the second input of the comparator.