A drive system has a number of electrical machines. One machine operates as a generator supplying an output to a DC link, which in turn supplies one or more machines operating as motors to drive loads. The motors are supplied through power converters. The total capacitance of the DC link is minimised and the link kept in a stable condition by preventing it falling to a hazardous level. One embodiment prevents the phase currents adding in such a manner as to reduce the DC link voltage. Another embodiment employs freewheeling in the phase currents to prevent the DC link voltage falling below a predetermined threshold.