A new control scheme for series-parallel compensated UPS system

This paper describes a new control scheme using synchronous reference frame (SRF) of a three-phase series-parallel compensated UPS system in detail. By controlling the series converter as a sinusoidal current source in phase with the input voltage and the parallel converter as a sinusoidal voltage source in phase with the input voltage, the proposed control scheme can make this kind of UPS carry out all of the control goals: sinusoidal input current with cos φ=1 and sinusoidal output voltage with normal value in the case of nonsinusoidal, nonnormal supply voltage and nonlinear load. Digital simulation results are presented to verify the good performance of the UPS system and the effectiveness of the new control scheme.