An apparatus and method for controlling the delivery of a pre-determined amount of power from a DC source to an AC grid includes an inverter and an inverter controller. The inverter includes an input converter, an energy storage capacitor, and an output converter. The inverter controller includes an input converter controller and an output converter controller. The input converter controller includes feedforward controller configured to perform a calculation to determine a value for the duty cycle for the input converter such that: (1) the input converter delivers the pre-determined amount of power and (2) the magnitude of a ripple signal reflected into the input source is attenuated toward zero. The input converter controller may also include a quadrature corrector configured to determine the effectiveness of the calculation in attenuating the ripple and to adaptively alter the calculation to improve the effectiveness.