The frequency converter is a core component of fractional-frequency transmission systems. However

in special environments with high salinity and humidity

the reliability of existing power electronic frequency converters is significantly reduced

leading to increased operation and maintenance costs

limiting the application of fractional-frequency transmission systems. To address this issue

we studied the ferromagnetic frequency converter for fractional-frequency transmission systems. First

based on the principle of the magnetic frequency tripler

the principles for the core and winding structure were analyzed. A three-phase magnetic frequency tripler topology was then developed by introducing a phase-shifting winding on the primary side. Next

the effect of ferromagnetic saturation was taken into account

and a model of the magnetic frequency tripler incorporating strong nonlinearity was established. In combination with field-circuit coupled finite element analysis

a design method for the three-phase magnetic frequency tripler was proposed. Based on the theoretical investigations above

this study developed both a laboratory and an engineering prototype of the three-phase magnetic frequency tripler

achieving efficiencies of 92.8% and 94.8%

respectively

and improving the power quality. Moreover

the grid-tied test of the three-phase magnetic frequency tripler was conducted

verifying the effectiveness of the proposed analysis.