Synchronous-frame harmonic control for high-performance AC power supplies

In order to achieve the reduction of voltage distortion in ac power supplie s (ACPSs), this paper describes an implementation of synchronous-frame cont rol for selected frequencies in the output voltage. The regulation of the f undamental output voltage, as well as that of some low-order harmonics, is achieved using a synchronous-frame controller for each selected frequency i n addition to a conventional control, The conventional part conserves good dynamic performance under load changes, while rotating-frame controllers al low a slow, but very precise compensation of the residual errors within the assumption that the harmonics produced by distorting load are slowly varyi ng, Moreover, motivated by a fixed-point implementation, a set of refinemen ts and modifications of the original scheme is proposed, allowing a reducti on of signal processing requirements and a new control algorithm structure less sensitive to quantization and rounding errors. This solution is partic ularly effective for high-power fully digitally controlled ACPSs, where the voltage loop bandwidth is usually not large enough to provide regulation a t harmonic frequencies. The proposed control scheme has been implemented us ing a fixed-point single-chip digital signal processor (ADMC401 by Analog D evices), Experimental results on a 3-kVA three-phase converter prototype sh ow the effectiveness of the proposed approach.