Research On Modeling And Control Strategy Of DC Microgrid

With the increasingly serious problems of energy crisis and environmental pollution,more and more renewable energy sources have been exploited.In order to make better use of distributed energy and reduce its impact on the power grid,the concept of microgrid is proposed.At present,DC microgrid has become a research hotspot due to its low energy loss and high power quality in the research of microgrid.In this context,the paper takes the dc micro-grid as the research object,and mainly analyzes and verifies the modeling of each unit in the system,the micro-source control strategy and the coordination control at the micro-grid level.At the first,the paper introduces the structural of the DC microgrid and analyzes the mathematical model of photovoltaic cells,wind turbines,batteries,and each microsource interface circuit.The photovoltaic output characteristics were verified by simulation.The next,control strategies of each micro-source device are analyzed,and different control strategies are adopted for different micro-source devices.The working principle and application of each control strategy are introduced.The control strategy used by each micro-source device is simulated.The results show that each micro-source is stable under its own control strategy.Finally,a hierarchical coordinated control strategy based on DC bus voltage is proposed in the DC microgrid system.The advantage of this coordinated control strategy over traditional control methods is that the local information can be used to achieve self-control and management of system energy,improving system stability.According to the DC bus voltage,the system is divided into four working conditions.When the DC bus voltage changes,each micro-source device switches state according to the magnitude of the DC bus voltage,thereby keeping the system in a stable state.The Matlab/Simulink software is used to verify the system in the grid connection,offgrid and fault conditions.The results show that the various operating conditions are switched rapidly under different status,and the DC bus voltage is maintained within 5% fluctuation range,which meets the requirements of power consumption,which proves the effectiveness and feasibility of the proposed strategy.