1.National Key Laboratory of Power Transmission Equipment Technology (Chongqing University), Chongqing 400044, China;2.College of Electric Engineering, Sichuan University, Chengdu 610065, China

The DC transformer (DCT) is the key equipment for achieving interconnection of multi-voltage level DC distribution networks, and its control strategy is crucial for the efficient operation of the system and power quality. This paper proposes an optimal operation strategy for DC distribution network that takes into account DCT control switching. Firstly, the topology and control methods of DCT are introduced, and the voltage-current transfer matrices of DCT ports under different control modes are derived. On this basis, combined with network constraint equations, a simplified model of DC distribution network with DCT is established, and the impact of different control modes of DCT on network operation is analyzed. Then, the DCT port transfer matrices in different control modes are embedded into the current calculation equations, and a multilevel DC distribution network optimization strategy is established with the objective function of minimizing system losses, taking into account the constraints of grid safety and energy storage, and the solution process is given. Finally, the effectiveness of the optimal strategy proposed in this paper is verified by using a modified IEEE DC distribution network case.

This work is supported by National Natural Science Foundation of China (No. 52077017).