Active Power Distribution System between Phases of the Transformer’s Converter

The paper proposes the system that distributes automatically active power between phases at the secondary side of a traction transformer-based converter. The application area for this system is ac railways with big volumes of delivered items. The purpose of the paper is to develop and investigate the equivalent circuit of the proposed system as an electrical complex for automatic power distribution between phases of the transformer-based converter with phases of the rail-way traction power system at the secondary side. The equivalent circuit of the mentioned above electrical complex is stated. The expressions describing the process of automatic distribution of active power are based on the instantaneous power theory. It is shown how the unbalance factor and total harmonic distortion depend on the number of switching element cells at each phase and pulse-width modulation switching frequency. As it follows from the simulation, the pro-posed electrical complex should consist of eight cells of switching elements connected to each phase to provide values of the unbalance factor and total harmonic distortion no more than two percent. The pulse-width modulation phase has to be a multiple of 45 degrees. The most im-portant result is the proposed equivalent circuit of the system for active power distribution be-tween the transformer-based converter phases at its secondary side, distinguished by the capabil-ity of getting the optimal number of switching element cells by simulation based on the instantaneous power theory. The results relevance include improvement of the electric power quality indicators such as unbalance and total harmonic distortion and decrease of wear factor values for transformers and transmission lines.