SU731549A1 - Method of control of multiphase power-diode frequency converter - Google Patents

Description

one

The invention relates to methods of controlling frequency frequency converters based on autonomous inverters and can be used in multiphase converter plants where parallel or continuous connection of valves is required, for example, in a mopd, and a frequency-controlled electric drive, autonomous power sources.

Known methods for controlling frequency converter converters containing l parallel or series-connected three-phase bridge inverters, in which, to improve the harmonic composition of the output signal, separate inverters are controlled with a phase shift and then their output signals 1 are summed.

The disadvantage of this method is 20 great complexity.

Of the known methods, the most promising approach to the invention is a method of controlling a multiphase vent converter with a three-phase output, containing 25 parallel or serially connected three-phase bridge inverters, consisting in that the inverters are controlled synchronously with a phase shift of / 3 rad 2.30

At the output of each of the inverters included multiwinding transformers, the secondary windings of which are made with different coefficients of transformation.

Due to the phase shift in the control of the individual inverters and the corresponding switching circuit of the secondary windings of the transformers, a three-phase arc-shaped voltage is formed at the output of the device. The voltage levels of the secondary windings of the output transformers determine the magnitude of the steps in the output voltage and its harmonic composition.

The disadvantages of this method are the presence of harmonics of the order of / ((6 / g ± 1) and multiples of nm, as well as high power consumption, in the output signal.

The purpose of the invention is to improve the quality of the output signal by means of harmonics of the order of K (Qn ±) and multiples of them, and also reduce the amount of my favorite flash power;

This is achieved by the fact that in a known method, at each of the η mismatch intervals in phase of the output signals of said inverters, they vary the amplitude of their input signal, but according to the law

° - pYH

-RP GR

where http is relative change

amplitudes;

, 2, ... ha - is the order number of the terminal.

The drawing shows an electrical block diagram of a device implementing this control method.

The power part of the device includes a controlled rectifier 1, fed from the mains, and a series of parallel or serially connected autonomous inverters 2, to the outputs of which a three-phase load 3 is connected. The control system includes a master oscillator 4 that converts the Vf signal in frequency in the sequence of pulses; phase shifting device 5, which generates the signals of oscillator frequency 4, phase-shifted by / zl rad; a series of distributors 6 control units of autonomous inverters, to the inputs of which the outputs of circuits 4 and 5 are connected; a device 7 for phase-pulse control of a rectifier; output control knob 8 capacitor 1 (inverter input signal 2); switching device 9, which jumps the setpoint of the signal for setting the output signal of the converter in dependence on the signal of the device 5.

The output waveform of the multi-phase converter during the period of the output frequency is a 6 / g-pitch curve. In one of the sections / S glad, during the interval / 3 I am pleased, the output signals of all n inverters coincide in phase, in the remaining sections they do not coincide.

According to the proposed method, on the phase mismatch intervals of the output signals of all inverters, the amplitudes of these signals are simultaneously and appropriately changed relative to their amplitudes in the common-mode interval. The modified amplitudes are made by varying the magnitude of the input signal of the inverters with its regulator. The relative magnitude of the amplitude jumps is chosen based on the fact that the resulting 6 "-stunent shape of the converter output signal does not contain harmonics of the order of / ((6 ± 1) and multiples of them (except

main), therefore, relative amplitude change during transition from site to site is carried out in accordance with the expression

Ylf-pn /) 2

Where

n is the number of sections corresponding to the number of cascade connected inverters;

p 1,2, ... dpor dky died the plot. Using this method of control of a multiphase frequency converter allows you to completely eliminate the low harmonics in its output signal curve by means of control tools without any complicated power circuit and equipment set power.

Claims (2)

1.Bedford B., Hoft R. Theory of autonomous inverters. M. Energie, 1969, p. 180- 188, 201-203. 2. Patent SShg L 3521143, cl. H 02M 7/30, 1970.