A Novel Waveform Modulation Method for Staircase Inverters

The staircase inverters are suitable for high power rating applications due to their low switching frequency and perfect harmonic performance. Because the switching signals are generated with delaying method traditionally, the dynamic regulation is poor. A novel waveform modulation technique for the staircase inverters is proposed in this paper, which adopts sequential sampling Space Vector Modulation (SVM) technique to generate all the switching signals, therefore the bandwidth of the inverters is enlarged. Based on the analysis of effects on the six basic vectors of each inverter bridge by phase-shifting transformers, a special sample sequence of SVM, which is from lagged bridge to the leading one, is proposed to meet the logic requirements of gating signals. The spectrum of output waveform and the characteristics of this modulation technique are analyzed. Simulation and experiment results prove that this modulation technique can be used to regulate the output of the staircase inverter with excellent output spectrum, and the bandwidth of the inverter is extended, which is helpful for improving the inverter's dynamic performance.