Power Control of a Modular Three-Port Solid-State Transformer With Three-Phase Unbalance Regulation Capabilities

Three-phase unbalance issue can cause adverse impacts on the power quality of the solid-state transformer (SST) based AC/DC hybrid microgrid. In this paper, an unbalanced power control strategy for cascaded dual active bridge (DAB) converter is proposed. With the strategy, the transmitted power of each DAB module in each phase is evenly distributed in terms of the three-phase unbalance degree of the three-phase AC grid. Thus, the idea of unequal power sharing in cascaded DAB can be applied to mitigate the three-phase unbalance from the perspective of power control. Moreover, this paper proposed a three-phase unbalance power mitigation algorithm based on the unbalanced power control strategy for the cascaded DAB. The proposed strategy can help the SST realize the function of mitigating three-phase unbalance when it transmits energy to the DC microgrid. Thus, the proposed control strategy can mitigate the three-phase unbalance on the premise that the power demand of the system is met. Finally, the simulations and the experiment results have verified the effectiveness and correctness of the proposed control method.