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An adaptive controller for the compensation of output voltage ripple due to harmonic distortion in the input voltage is proposed for a pulse width modulated (PWM) boost converter. Following the Lyapunov approach, we designed an adaptive law to cope with uncertainties in the disturbance signals and parameters. Complexity of the proposed controller is reduced by rotations which transform the adaptive terms into a sum of resonant filters tuned at the frequencies of the harmonics under compensation, and operating on the output voltage error. To facilitate the implementation, we have tried to preserve the structure of the proposed controller as close as possible to the conventional one, which includes a voltage outer loop (basically a proportional plus integral (PI) control on the output voltage error) and an inner control loop (basically a proportional control plus a feedforward term). In the proposed controller, the bank of resonant filters appears as a refinement term added to the inner control loop. Indeed, they insert notches in the audio-susceptibility curve, which are tuned at the harmonics under compensation. Thus, in addition to the benefits of a conventional feedforward PWM control, the bank of resonant filters are able to cancel selected harmonics. Experimental results on a boost converter board, using a poorly regulated voltage source, are presented to assess the performance of our approach.