Voltage control and fluctuation suppression of the three-phase SST with DC bus in dual rotating reference frames

The three-phase solid-state transformers(SST) with DC bus have been widely studied in micro-grid systems. The double line frequency component of AC power on DC-link in SST is unavoidable because of the inherent single phase structure of the HV-side cascaded H-Bridge(CHB) converter. However, the AC power at double line frequency of three phases can be mutually eliminated by enabling DAB converters with the ability to process the power. This paper develops a closed multi-loops method of voltage control and fluctuation suppression for the three phase SST system with DC-bus in dual rotating reference frames. Theoretical analysis and modeling are provided. The performance of the proposed control strategy is verified through simulation results and the experiment is under way.