Tap for Classical HVDC Based on Multilevel Current-Source Inverters

This paper describes an innovative HVDC tap design based on series connections of current-source capacitor-commutated thyristor modules. Besides immunity from commutation failure and autonomous frequency control, the tap has independent active and reactive power control. There is potential of cost reduction because the number of thyristors is reduced by one-third. Switching loss is minimum as the modules switch at 2 pulses per ac cycle. Harmonic elimination by “time shifting and zig-zag transformers” achieves a current total harmonic distortion of about 4%.