DIRECT FREQUENCY CONVERTERS WITH QUASI-SINGLE-SIDEBAND MODULATION WITH SINGLE-PHASE AND THREE-PHASE SEMICONDUCTOR DOUBLE-ACTING SWITCHES

Abstract

The article examines circuits of multiples of three multi-pulse three-phase-three-phase direct frequency converters with quasi-single-sideband modulation related to direct frequency converters with artificial commutation, in the valve block of which fully controlled double-acting keys are used.

In this case, both single-phase bridge and three-phase bridge fully controlled double-acting keys are used as fully controlled double-acting keys.

For the analysis, derivation of the main relationships linking the input and output voltages and frequencies in these converters, as well as their comparative evaluation, methods of harmonic analysis and switching functions (switching functions) are used, taking into account the generally accepted assumptions (current commutation in valves is instantaneous, active losses in all elements of the circuit are zero, the magnetization current of the transformer is zero, the transformation ratio is 1, the three-phase voltage at the input of the converter is sinusoidal).

It has been shown that in such converters, when using three-phase bridge fully controlled double-acting switches instead of single-phase bridge switches, the total number of switches used is reduced by three times, the total number of fully controlled semiconductor devices with one-way conductivity is also reduced by three times, and the total number of power uncontrolled semiconductor devices with one-way conductivity is reduced by two times.

The ranges of relative values of the fundamental harmonic output frequencies at which DC components and subharmonics may be present in the output voltage are presented.

It is shown that with increasing output voltage pulsation, the distortion factor (harmonics) of the output voltage decreases, while simultaneously increasing the range of output frequencies in which DC components and subharmonics are absent.