A polyphase alternating current (AC) active rectifier system converts polyphase AC from an AC source to direct current (DC) on a DC bus comprising a positive DC bus line and a negative DC bus line with a switching element for each phase configured to direct current from the AC source to the DC bus through four different conducting paths with three electrical potential levels, including a positive DC level on the positive DC bus line, a negative DC level on the negative DC bus line and a neutral DC level between the positive and negative DC level on a neutral DC bus line and suppresses AC common mode electrical potential from the DC bus, comprising: a ground path between the neutral DC bus line and a system ground coupled to a neutral point for the AC source that clamps the level of the neutral DC level to the AC source neutral.