In order to maintain a high quality output voltage, conventional UPS systems use complex filters with large passive components. To overcome this drawback, real time feedback control schemes have been investigated. However, these techniques require a high inverter switching frequency to dynamically adapt to changing load conditions and reduce harmonics of the output voltage, thereby rendering the system inadequate for high power applications. This paper presents real time digital signal processor (DSP) control of a UPS system feeding nonlinear loads to provide sinusoidal inverter output voltage. The control scheme is composed of an rms voltage regulator, the load current harmonics regulator for the cancellation of output voltage harmonics, and the output voltage harmonics regulator for system stability. The controller employs a Texas Instruments TMS320C40GFL50 DSP.