Development of a 1.5 MW, Seven Level Series-stacked Converter as an APF and Regeneration Converter for a DC Traction Substation

A prototype 1.5 MW series-stacked converter system was built and installed at a DC-traction substation. The converter inverts energy generated by slowing an electric train using regenerative braking. The regenerated energy is fed into the local AC network at the DC-substation. A secondary function of the converter is to perform active power filtering (APF) while a train is drawing power from the substation. The systems control is based on the instantaneous reactive power theory. An interleaved switching scheme is used to switch the seven level series-stacked converter, thus exploiting the natural balancing properties of the series-stacked converter. Results obtained from tests done show that both the APF and regeneration functions of the system were successfully implemented