Collaborative optimization control of hybrid distribution transformers integrated with photovoltaics in unbalanced distribution networks

This paper proposes a novel hybrid distribution transformer integrated with photovoltaic (HDT–PV) including a three-phase four-leg inverter, as a promising electrical device applied in the unbalanced active distribution network (ADN). The HDT–PV has the ability to access distributed PV system, balance three-phase power and provide reactive power compensation. In order to take advantage of these capabilities of the HDT–PV, collaborative optimization control strategy of HDT–PVs in the unbalanced ADN is presented. The optimization aims at minimizing network power losses and improving voltage profiles of the entire ADN. To do so, the HDT–PV's model in the case of unequal three-phase loads is established, and the corresponding simulation is conducted to verify the correctness of the model. Finally, case studies of collaborative optimization control of HDT–PVs are carried out in various scenarios using the modified unbalanced IEEE 33-bus system. The results verify the effectiveness of the proposed collaborative control scheme on reducing network power losses and suppressing three-phase voltage unbalance.