A solid-state transformer comprises a plurality of power units (100). Each of the plurality of power units (100) comprises a high-voltage side module (110), a low-voltage side module (120), and an isolation transformer (130). The isolation transformer (130) comprises a high-voltage winding (131), a low-voltage winding (132), and an iron core (133). The high-voltage winding (131) is wound on the iron core (133) and connected to the high-voltage side module (110). The low-voltage winding (132) is wound on the iron core (133) and connected to the low-voltage side module (120). The iron core (133) is in near equipotential connection to the high-voltage side module (110) or the low-voltage side module (120) by means of a conductive medium to fix the floating potential of the iron core (133).