Increasing the Pulse Number of AC-DC Convertors by Current Reinjection Techniques

A general method is described to determine a current waveshape which, when injected into a six-pulse convertor transformer secondary, increases the pulse number of a convertor bridge. The current injection is derived from the ripple of the rectified voltage and a single phase feedback convertor; the latter is connected in series with the dc output of the main bridge. The circuits needed to achieve the required current feedback are developed for twelve and twenty-four pulse generation. Practical considerations lead to the development-of a considerably simpler configuration that provides quasi twenty-four pulse operation and the theoretical waveforms are verified experimentally.