Lager-scale non-grid-connection wind power theory avoids the technical issue of integrating wind power into utility. This paper introduces a novel system structure based on the DC grid for the large scale non-grid-connection wind power application. The system is especially suitable for the wind power generation system where full power conversion and high energy consumptive DC load is used. The proposed system has the merits of less power conversion train， simple structure， low power losses and high reliability. Then， a bus voltage step control strategy is proposed for the DC micro-grid system. By using the control strategy， not only the normal operation requirement of terminal devices is guaranteed， but also the power exchange between wind power system and utility is minimized. Finally， a system model is established with Saber simulator， and the simulation results verify the feasibility of the proposed system and its power control strategy.