Research On Control Strategy Of Micro-grid Inverter Integrated Photovoltaic And Energy-storage

Solar energy is widely used in distributed generation(DG) as it is the most extensive and clean energy, the development of the DG system promotes the development of micro-grids. In order to make the use of micro-grid more flexible and efficient, energy-storage equipment is necessary. So it has important significance to study the control strategy of micro-grid integrated photovoltaic and energy-storage and its optimal control methods.Firstly, this thesis introduced the structure of micro-grid integrated photovoltaic and energy-storage, in which the PV cells and the battery were both connected as input sources only by a two-stage inverter. Then on the basis of this structure, the control schemes both in islanded and grid-connected mode were designed, the control parameters were designed as well. The unbalanced load would cause the asymmetric output voltage in isolated mode, so the cause of the unbalance was analyzed in theory, and a control method of proportional integral plus resonant for unbalance control was introduced. When the micro-gird operated in grid-connected mode, the grid current quality was affected by grid voltage. On the basis of the traditional proportional-integral control, a loop of harmonic suppression based on multi resonant controller was added in to improve the quality of grid current. At the same time, the simulation model of micro-grid is built in Matlab/Simulink software was depicted to verify the feasibility of the unbalanced control and harmonic control. Finally, a 15 kVA micro-grid inverter integrated photovoltaic and energy-storage was designed and is built to evaluate the full function for micro-grid.The experiment results also verified the feasibility of the unbalanced control in islanded mode and grid current harmonic control in grid-connected mode.