The invention concerns a power control apparatus and a method for supplying power between an electric machine and an energy source. The power control apparatus contains at least two converters comprising a plurality of switches, at least some of which switches belong to a set of switch modules comprising a plurality of switches. In the method of the invention, a first set of switches belonging to at least two different modules and arranged to form a first converter is controlled by a first converter control, and a second set of switches arranged to form a second converter is controlled by a second converter control.