Resumen
In order to minimize the reactive power and higher harmonics of currents, as well as to improve the electromagnetic compatibility of electrical traction networks and systems of railroad automation, modern electric rolling stock of alternating current employ active four-quadrant rectifiers. The classical topology of a given converter is the two-level full-bridge active rectifier that ensures a power factor close to unity and the recuperation of energy to a power network. However, the high switching frequency predetermines high dynamic losses in power transistors and a low value for efficiency.It appears promising to use the three-level active four-quadrant rectifiers with a power factor correction. It has been proposed in the current work to apply a system of control over a three-level active rectifier with the two-channel equal-shifted sinusoidal PWM. The advantage of the proposed algorithm, as compared with known, is the improvement of quality of the input current and a decrease in the frequency of switching power switches, which leads to a decrease in power losses and an increase in the rectifier efficiency. The paper reports results of comparative analysis of dependences of power losses and efficiency on the switching frequency of power switches for the two-level and three-level active rectifier with the proposed control system, which confirmed the feasibility of the proposed control system. The software package MATLAB 2017b was used for simulation modeling of the two-level and three-level active rectifier, based on which we analyzed the quality parameters of electric energy, established the dependence of a harmonic distortion coefficient of the input current of an active rectifier on the switching frequency of power switches. Our study has proven the technical and economic expediency of using a circuit of the three-level active rectifier with a control system based on the two-level equal-shifted sinusoidal PWM.