Improved control scheme towards reduced DC link inductors in a Multi-Cell Topology based on Current Source Converters

The main drawback of a Multi-Cell topology based on Current Source Converters is the oscillating power drained by the single-phase inverters from the DC link which requires a large DC reactor in order to avoid a significant variation of the DC current. In this work, a control scheme is proposed in order to compensate the oscillating power, avoiding to oversize the DC reactor at the expense of increasing the distortion of the input currents in each power cell and the instantaneous peak of the modulation index. However, the overall input currents present very low distortion and the instantaneous peak of the modulation index can be reduced by properly designing the multi-pulse transformer in terms of voltage ratio and phase shift. Both, the input currents distortion and the effect in the modulation index are mathematically characterized. Simulation result illustrates the effectiveness of the proposed control approach.