A transformerless compensator used in traction substation for load balancing

Most converter-based power conditioner schemes for traction substation so far contain a pair of costly and bulky step-up transformers. A transformerless compensator is proposed in this paper to balance the loads of traction supply arms. This novel compensator employs a neutral-point-clamped three-level three-leg converter based on series connected IGBTs. Dynamic voltage balance of IGBTs is carried out by a slope regulating and peak clamping way. And a virtual three-phase control strategy is designed for such a converter so that the compensator is capable of delivering bidirectional active power, providing reactive power for each supply arm and at the meanwhile maintaining dc-link voltage constant. Experimental results about dynamic voltage balancing and simulation waveforms about power conditioning are presented which validates this novel transformerless compensating solution.