Key Technology Research On Micro-gridinverter Based On Repetitve Control

With the energy crisis and environmental problem which is getting worse, the distributed power generation(DG) is undergoing a significant development all around the world. Although the DG is flexible, friendly to the environment and has the advantage of high efficiency, large-scale integration of DG may introduce some negative effects on the operation stability of the utility grid. Microgrid can not only solve the problem of large-scale DG integration, but also play full advantages of DG and improve reliability of power supply and bring benefits to customer. As a microgrid inverter is the basic power electronic interface unit in microgrid, the control strategies of microgrid inverter is directly related to the stable operation of the microgrid.In this thesis, the mathematical modeling of micro-grid inverter has been derived, and the design of its traditional control loop is depicted. The unbalanced load may cause the asymmetric output voltage in the island mode, so the essential causes of the unbalance is analyzed in this thesis. A method of micro-grid control based on repetitve control is introduced to achieve unbalance control of the output voltage under the condition of island operation mode. On the basis, a dual-mode-structure repetitive control is adapted to improve the dynamic performance. When the microgird is working on the grid-connected mode, due to the effect of hardware and external disturbance, the grid current quality can not meet the standard. In this thesis, a method of microgrid control based on repetitve control is used to improve the steady-state tracking accuracy and harmonic suppression. On the basis, in order to improve the dynamic performance, a method of T/6 repetitve control is adapted. Furthermore, the simulation model of microgrid is built by the Matlab/Simulink software to verify the feasibility of unbanlanced control and the control of grid current. Finally, a digital control based 100 Kva experimental phototype of microgrid inverter is built. And the software design of the microgrid inverter is introduced. The experiment results are depicted to verify the feasibility of the microgrid inverter with the repetitve control.