A modified parallel HVDC convertor for 24 pulse operation

A new concept in power convertor design suitable for large current ratings, such as those used in back-to-back HVDC interconnections, is proposed. It consists of a parallel 12-pulse configuration involving two phase-shifted bridges and a thyristor-tapped interphase reactor. The DC ripple present across the interphase reactor is used to derive a current waveform which, when added to the original phase currents, effectively doubles the converter´s pulse number. It is shown theoretically and experimentally that the use of DC-ripple reinjection achieves 24-pulse operation from a conventional 12-pulse HVDC converter configuration