Research On Control Strategy Of DC Microgrid With Photovoltaic And Storage System

ABSTRACT:With the increasing of human demand for energy and the increasingly decline of the coal, oil, natural gas and so on, people have realized the importance of the development of renewable energy. The key technology of using of renewable energy is how to integrate renewable energy into the power grid, and the microgrid technology can just solve this difficult problem. Put the distributed power and load as a whole, forming a controllable small grid, which can work both in the island mode and in the grid mode, which is called microgrid. Microgrid includes DC microgrid, AC microgrid and AC/DC microgrid, and the DC microgrid has the advantage of less energy transform link, simple structure, flexible control, which has already become a hot spot of the current research. However, different micro power has different features, how to coordinate the relationship between the micro power is the key to the microgrid. If the microgrid energy management problem is solved perfectly, it will protect the micro power, exert the advantage of micro power, and improve the performance of the whole micro power grid.The research object of this thesis is the DC microgrid which is consist of photovoltaic panels, battery and load. On this basis, a novel energy management control strategy is proposed for DC micro-grid, which combines the structure of the micro-grid and its integrated control objectives, it designs the system control strategy under grid pattern and island model. In the grid pattern, it uses the grid to maintain the stability of the dc bus voltage, PVs work in the maximum power tracking mode all the way, it uses the difference between the PV power and the load power to control the battery. When the grid is abnormal, the system can switch to island mode automatically. In the island pattern, the PVs can work in the MPPT mode or the constant voltage mode, and the battery can work in the boost mode or the voltage stability limit current mode. In this thesis, by controlling the current of the battery to realize smooth switching between the different models.The thesis used the simulation model and experimental platform of the DC microgrid with photovoltaic and storage system, through increasing or decreasing the load at DC bus terminals and changing the state of the synchronizing switch to detect the stability and reliability of the system. The simulation results show that this control strategy not only maintains the stability of the DC bus voltage, but also realizes the smooth transition between the two kinds of mode, which meets the requirements of the system.