This work deals with the problems of uninterruptible power supplies (UPS) based on the single-phase to three-phase converters built in two stages: an input bridge rectifier and an output three phase inverter. The two blocks are joined by a continuous intermediate bus. The objective of control is threefold: i) power factor correction “PFC”, ii) generating a symmetrical three-phase system at the output even if the load is unknown, iii) regulating the DC bus voltage. The synthesis of controllers has been reached by two nonlinear techniques that are the sliding mode and adaptive backstepping control. The performances of regulators have been validated by numerical simulation in MATLAB / SIMULINK.