RESEARCH INTO ENERGY CHARACTERISTICS OF SINGLE-PHASE ACTIVE FOUR-QUADRANT RECTIFIERS WITH THE IMPROVED HYSTERESIS MODULATION

The traction electric drives for electric rolling stock of alternating current employ the diode and thyristor rectifiers that predetermine a series of shortcomings. These include the significant emission of reactive power and higher harmonics of currents to the contact network, as well as the impossibility of implementing electricity recuperation to the contact network. In this regard, it is promising to use single-phase four-quadrant active rectifiers with a correction of power coefficient. The advantage of these converters is ensuring a power coefficient close to unity, the implementation of the sinusoidal input current, as well as the possibility of implementing electricity recuperation to the power network. In the systems of control over active rectifiers quite common are the control systems with hysteresis modulation. However, hysteresis modulation predetermines the need to implement high and variable frequency for switching power keys, which negatively affects power losses in a transducer. Therefore, a control system with improved hysteresis modulation has been proposed. Due to the improved algorithm for switching power keys the proposed improved hysteresis control system makes it possible to reduce the number of switching power switches. That decreases the dynamic losses of power in an active rectifier, which makes it possible to improve the efficiency of electric rolling stock in general. The simulation modeling conducted in the MATLAB 2017b software has confirmed effectiveness of the proposed modulation algorithm. In addition, during implementation of the proposed commutation algorithm there is an improvement in the harmonic composition of input current. The reduction in the amplitudes of higher harmonics of input current has been confirmed, as well as the improvement in the resultant coefficient of harmonic distortion