A power conversion system (10) comprising a plurality of modules (14) each having an input (16) and an output (17) and being connected in series. Each module (4) is connected to at least one DC power source (12) that supplies power to the module (14). Voltage control circuitry provided within each of the modules (14) to vary the voltage supplied between the input (16) and the output (17) between a maximum module voltage and a minimum module voltage. A control unit (29) in communication with the voltage control circuitry of each of the modules (14) varies the voltage supplied across the input (16) and output (17) of each of the modules (14) such that the total voltage across the series connected modules (14) forms an AC signal or a rectified version of an AC signal.