In this paper is proposed a nonlinear control for fuel cell/battery/ultracapacitor hybrid power sources (HPS) that improves the performance and durability of fuel cell. The nonlinear voltage control is analyzed and designed using a systematic approach. The design goal is to stabilize the HPS output voltage at a low voltage ripple that is also spread in a large frequencies band. All the results have been validated in several simulations. The simulation results successfully show that nonlinear voltage control performs good performances in the frequency-domain (a high spreading level of power spectrum) and in the time domain (a low level of output voltage ripple factor), too.