Analysis of the network current in circuits of twenty-four pulse controlled rectifiers

Abstract

The main part of the electric power is consumed in a transformed form and the use of semiconductor converter circuits for obtaining the specified parameters of the load increases. As part of energy savings, the requirements for the quality of semiconductor converters, their impact on the supply network, the load and related consumers are increasing. To convert AC voltage to DC widely used circuits, made on the basis of single-operation thyristors. Their significant drawback is poor electromagnetic compatibility with the supply network. To improve it and increase its efficiency, multi-pulse rectifier circuits are used. With a high load power, as well as when special requirements are imposed on the harmonic composition of the output voltage and current consumed from the network, twenty-four-pulse controlled rectifier circuits can be used, which can reduce power losses not only in rectifiers, but also in power supply networks and adjacent consumers due to reducing the effect of distortion on the quality characteristics of networks from the non-linear load, which is the rectifier. In proportion to the increase in the pulsation of the rectified voltage, the weight and size and cost parameters of the smoothing filters in DC networks are reduced. In this paper, a computer simulation of the symmetric and asymmetric circuits of twenty-four-pulse controlled rectifiers was performed. Analysis of the simulation results showed that with the same number of ripples in the output voltage and full symmetry of the circuits in terms of load, the shapes of the network current curves are different. When conducting a virtual experiment, it became obvious that for an asymmetric scheme the amplitudes of higher harmonics in the entire range of control angles are consistently lower than the amplitudes of harmonics for a symmetric scheme and the asymmetric scheme is promising for practical use, despite the need to use two different types of transformers.