Modified Modulation Techniques for Quasi-Z-Source Cascaded H-Bridge Inverters

Quasi-Z-source cascaded H-bridge (qZS-CHB) inverters are one promising solution for high power photovoltaic (PV) systems. This type of topologies inherits the advantages of cascaded converters (i.e., multilevel outputs) and impedance-source inverters (i.e., high conversion ratios). In addition, it allows increasing the inverter reliability (with high redundancy). However, the modulation and control of qZS-CHB inverters are challenging to a certain extent. Thus, this paper proposes modified modulation techniques to increase the performances of qZS-CHB converters in terms of voltage gains and stresses. The novelty lies in the use of the switching frequency optimal as reference signals in the modulation techniques. A comparison in terms of harmonics with selected modulation techniques is performed.