Towards a zero-output impedance UPS system

A categorization of loads requiring clean uninterruptible power is provided, a thorough analysis of their effects is given, and presently used partial solutions are examined. The topology of a low-impedance 3-φ high-power inverter stage, designed to alleviate substantially the current difficulties faced by interruptible power supplies (UPSs) when dealing with unbalanced and/or nonlinear loads, is described. On the basis of theoretical and extensive experimental results, it is concluded that the low-output-impedance 3-φ UPS presented performs well under both unbalanced and nonlinear load application