Challenges of Traction Single-Phase Current-Source Active Rectifier

This paper deals with single-phase current-source active rectifier (CSAR) dedicated for retrofitting of older types of dc machine locomotives and also for the new generation of traction converters employing medium-frequency transformer. A summary of main tasks of the converter operation and proposed solutions will be presented in this paper. Required CSAR behavior have been: (i) the operation on both ac electrification systems of 25kV/50 Hz and 15kV/162/3 Hz, (ii) "sinusoidal" trolley-wire current waveform, (iii) control of phase shift between trolley-wire voltage and current even in nonzero area in order to provide a reactive power compensation feature, and (iv) improved behavior under distorted trolley-wire voltage conditions. We have developed three control strategies which satisfy above described demands. Proper function of proposed controls has been verified by simulations and large experimental study made on designed laboratory prototype of CSAR of rated power of 7kVA.