| With the world energy crisis and environmental pollution problem becoming serious, the development and utilization of renewable distributed energy draws more and more attention. To avoid the impact when distributed power systems connecting to grid, usually make distributed power systems forming micro-grid when connecting to the grid. DC micro-grid is a system using DC distribution, which has the advantages of easy to control, high reliability, high efficiency and low line loss. To ensure the balance of power system and to realize load allocation is one of the most important aspects of the dc micro-grid control. Thus, research and analysis is conducted on the current-sharing control method of DC micro-grid.Firstly, this paper presents the design criterion and performance requirements of micro-grid, and DC converters is designed and completed based on the criterion. Half-bridge DC-DC converter topology is chosen and the small signal mode of converter is set up, based on which digital PID controller is designed to improve the static and dynamic performances of the converter.Secondly, common load-sharing methods are compared and the traditional droop method is analyzed emphatically. Traditional load current-sharing control method of dc micro-grid has two limitations. Dc-bus voltage deviation increases with load due to droop action; current sharing accuracy is degraded considering line resistance. In order to overcome the limitations of traditional droop control, the adaptive droop control method based on CAN bus is proposed. The whole control scheme is designed concluding CAN communication, software and hardware design.Finally, the simulation is made based on Matlab/Simulink to verify the analysis, experiment prototypes of two converters DC micro-grid are built as well. For various situations, different line impedance, different communication delay, load step change, converter access and cut out, the experimental results show the feasibility of the proposed control strategy. |
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