Patent ID: 6842354

Claim:
A power converter for producing an alternating voltage waveform for application to a load, said power converter comprising: a first voltage supply bus and a second voltage supply bus with a DC voltage there between; a plurality of capacitors connected in series between the first voltage supply bus and the second voltage supply bus and defining a neutral node; a DC to AC inverter connected to the first voltage supply bus, the second voltage supply bus and the neutral node and having an output terminal; and a controller which operates the DC to AC inverter to produce alternating voltage waveform formed by a sequence of output pulses having positive, zero and negative voltage levels in which a plurality of output pulses occur during each half-cycle of a modulating waveform, wherein the controller adjusts a width of output pulses during consecutive half-cycles of the modulating waveform in response to a difference in voltages between the neutral node and each voltage supply bus so as to compensate for that difference.