Active reduction of electrical machines magnetic noise by the control of low frequency current harmonics

A previous study has shown that the current low frequency harmonics, even with low amplitudes, have a strong influence on the global vibrations of a wound rotor synchronous machine. Therefore an harmonic dedicated regulation of the machine currents, allowing to manage in a low cost way their harmonic content, can drastically improve the acoustic noise of this machine. The main goal of this paper is to experimentally demonstrate the acoustic gain that could be attempted while decreasing the harmonic content of the currents using a harmonic dedicated regulation. A particular attention is given to the regulation of the 5th and 7th currents harmonics. The strong link between current harmonics and magnetic forces is theoretically introduced in the first part of this study, harmonic regulation principle is then detailed and finally experimental results present the important gains allowed by this technique.