Common-mode control for ac-to-dc power converters

A power converter apparatus comprising:

• a first power converter configured to receive a first AC voltage generated by a first electrical machine and output a DC voltage on a DC bus;
• a second power converter connected in parallel with the first power converter to receive a second AC voltage generated by the first electrical machine and output the DC voltage on the DC bus;
• wherein the first power converter is coupled to a first winding arrangement for receiving the first AC voltage and the first winding arrangement is grounded by a first impedance and the second power converter is coupled to a second winding arrangement for receiving the second AC voltage and the second winding arrangement is grounded by a second impedance, wherein the first impedance has an effective impedance value which is different to that of the second impedance such, in use, a zero-sequence current between the first and second power converters at least partly cancels a common-mode voltage component.