Discontinuous Modulation of Cascaded H-Bridge StatComs Considering Capacitor Voltage Oscillations

This paper formulates a discontinuous modulation (DM) technique for cascaded H-bridge (CHB) static compensators (StatComs) with star configuration. In the CHB StatComs, capacitor voltage (CV) oscillations cannot be disregarded when using relatively small dc-link capacitors. For this reason, in this paper, DM is achieved by injecting a zero-sequence voltage (ZSV) that takes into account the inherent CV oscillations. Then, the coupling that exists between the CV waveforms and the injected ZSV is analyzed. Particularly, the steady-state reference signals for the CHB StatCom operated discontinuously are analytically calculated. The practicability of the proposed DM technique is verified experimentally.