A new concept for the control of the harmonic content of voltage source converters

A new voltage source converter is proposed, based on the reinjection of the dc voltage via the neutral point of the double bridge converter. It differs from the conventional in that the voltage applied to the bridges varies, even though the dc voltage remains constant. To this effect a periodically varying waveform is supplied to the bridge and used to shape the ac side voltage into the specified waveform. The ideal reinjection waveform required for a complete elimination of the harmonic content is derived and then a practical approximation to the ideal suitable for the practical implementation is proposed.