Secondary voltage and current control strategy based on the DCT in true bipolar DC distribution network

In the true bipolar DC distribution network, due to the difference in cable impedance, the traditional bottom droop control has inherent contradictions between reducing voltage deviation and improving shunt accuracy, which affect the stability of the system and the economy of operation. Based on the underlying control, a voltage-current secondary control strategy based on DC/DC transformer (DCT) suitable for true bipolar topology is proposed. The control strategy is based on communication to collect the current of parallel DCT and the voltage of series DCT with different polarity. The consistency algorithm is adopted to achieve convergence of current control and voltage control, thereby achieving the optimal load distribution and effectively suppressing voltage imbalance. A true bipolar DC distribution network model is built by PSCAD/EMTDC. The simulation and evaluation results verify the effectiveness in diverse working conditions, adaptability to different topologies and reliability when a fault occurs in a distribution network of the proposed control strategy.