The invention relates to a control method and system intended to reduce the common-mode current in a power converter which comprises a rectifier stage (1, 1′) connected to a number of input phases (R, S, T) and an inverter stage (2, 2′) connected to a number of output phases (U, V, W). On each switching period, the rectifier stage (1, 1′) and the inverter stage (2, 2′) are controlled in a synchronized manner so that a variation of potential applied to an input phase (R, S, T) always corresponds to a variation of potential of the same sign applied to an output phase (U, V, W).