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An improved system structure and a corresponding protection system are proposed in this paper, which aims at providing future DC microgrids with suitable protection ideas. At first, the ring-bus system is adjusted to balance the system control and protection and make the system more conventional for the equipment expansion. In addition, based on this structure, a protection system is established. It consists of two parts, which are local protection and pilot centralized protection. The local protection is designed for protecting the vulnerable power electronic components in converters and the pilot protection is mainly proposed for the fault isolation. The combination between two parts makes the whole system overcome the contradiction between protection speed and reliability and the method also takes the protection suitability into consideration. Finally, all the methods are verified by the simulation system based on the PSCAD /EMTDC. [ABSTRACT FROM AUTHOR]