HYG series substation frequency conversion series resonance test device is mainly composed of frequency conversion control power supply, excitation transformer, reactor and capacitor voltage divider. The frequency conversion control power supply adopts imported SPWM digital waveform generator chip with 16 bits frequency resolution and 0.1 Hz frequency fineness at 20-300 Hz. At the same time, it adopts orthogonal asynchronous fixed carrier modulation mode to ensure good waveform output in the whole frequency range. The power part adopts advanced IPM module to ensure the stability and safety of the instrument.