THE SMOOTHING TRANSFORMER, A NEW CONCEPT IN DC SIDE HARMONIC REDUCTION OF HVDC SCHEMES

Direct connection schemes have been a subject of recent investigation, offering operational flexibility and substantial reductions in ac com ponents, In these schemes the use of active de filters has been sugges ted to replace the conventional tuned passive filter design. This pape r presents the smoothing transformer as a new means for reducing de ha rmonics at characteristic and non-characteristic frequencies using onl y passive components. A realistic smoothing transformer design is exam ined using the New Zealand HVdc system operating in the direct connect ion mode. The steady-state and transient performance of the smoothing transformer design is compared with that of the existing de smoothing reactor and filter bank.