Screening for HVDC system core saturation instability

Core saturation instability is a condition resulting from excess low-order harmonic ac/dc system interactions, amplified by increasing transformer flu x offset which, in turn, is driven by the interaction between the harmonics and the converter. A small signal analysis method has been successfully ap plied to efficiently screen a variety of conditions for core saturation ins tability, The screening measures have been defined in terms of the de syste m driving point impedances.