Control of Cascaded H - Bridge and Series Resonant Dual Active Bridge (DC-DC) based Solid State Transformer under Unbalance Grid

Due to the recent developments in power electronics, Solid State Transformer (SST) technology is now the preeminent solution for smart grid systems in generation and distribution networks. However unbalanced grid voltage conditions in the MVAC/LVAC grid can significantly degrade the power quality of SST. Due to the existence of negative components arising due to unbalance voltage in the grid, it produces oscillations in active and reactive power. Hence it is vital to design a control architecture to operate the SST proficiently under an unbalanced grid. This article introduces a control architecture to control positive and negative sequence currents in the LV and MV stages of SST independently. In the proposed technique, a current reference generation algorithm is introduced to suppress active power ripples at the MV/LV stage converter terminals. The proposed control architecture is validated in MATLAB Simulink on a 1.65 kV (MV)/500V(LVDC)/300V(LV), CHB-based SST.