Abstract
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.
Highlights
The input converters of electric rolling stock (ERS) of alternating current are most typically the diode and thyristor rectifiers
The aim of this study is to improve the energy efficiency of AC electric rolling stock by using the three-level active rectifiers under a traction mode, which is achieved by decreasing the emission of reactive power, by reducing the emission of higher harmonics of the input current and by abling it, which depends on the magnitude of current in a collector; EOFF(Iс) is the energy dissipated in a transistor at disabling it, which depends on the magnitude of current in a collector
Our study has proven the feasibility of using, for AC ERS, a circuit of the three-level active rectifier with a control system based on TES pulse width modulation (PWM)
Summary
The input converters of electric rolling stock (ERS) of alternating current are most typically the diode and thyristor rectifiers. For ERS, the circuit of the two-level active rectifier of switches must employ switches of a higher class (6.5 kV, or 4.5 kV) in terms of the rated voltage, which have, in comparison to switches of the lower class of voltage, the larger values of static and dynamic losses This leads to excessive power losses in a converter. The necessity for the formation of a high ever, the three-level circuit makes it possible to use switches switching frequency of power switches leads to rather large with a rated voltage that is two times lower It is the dynamic losses in the power switches with a lower efficien- unsolved technical task to study and substantiate the use cy in comparison with the diode and thyristor rectifiers. Of alternating current has not used a circuit of the three-level active rectifier
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