A unified feedback secondary control for bipolar-type DC microgrids with interlinking converter

In this paper, an interlinking converter and secondary control strategy for a bipolar DC microgrid are proposed to achieve inter-pole and full-domain current balance as well as bus voltage compensation. Compared with the traditional bipolar DC microgrid with independent operation of positive and negative poles, the coordinated operation of the bipolar converter is realized. Firstly, the designed high reliable interlinking converter and the corresponding control strategy enable voltage balancing function to achieve the inter-pole current equalization. Then, a unified voltage feedback secondary control is designed to achieve full-domain current sharing and bipolar bus voltage regulation under unmatched line impedance. Finally, a bipolar DC microgrid simulation model is established for testing. The results show that the proposed interlinking converter and secondary control can realize the control objectives under various operating conditions.