Research On Grid Connected Control Of Multi Inverter In Microgrid

In recent years,microgrid has been developing rapidly in the global power field.It belongs to the low voltage small power distribution network,mainly composed of micro power,load and control devices.The operation of microgrid system is mainly divided into two modes: microgrid isolated network mode and grid connection mode with microgrid and public power grid.However,when applying traditional control strategy,there will always be some unbalanced factors,which affect the stability performance of microgrid.In this thesis,the main problems in the operation of microgrid are studied on the background of the parallel network structure of the multi inverter in the microgrid.First,based on the resistance of line impedance in microgrid,we design a droop characteristic that can effectively satisfy multiple inverter microgrids by parameter control,and give the power equation of droop characteristic,effective implementation of power output allocation for multi inverter microgrid based on capacity is proposed.An improved droop control strategy is proposed to meet the stability of microgrid under different power systems.Secondly,the MATLAB of the grid connected based on the improved droop control is compared with the simulation.The comparison between the single and multiple inverters in the microgrid is carried out,which verifies the effectiveness of the multi inverter microgrid in the two modes of stable operation.Then,in order to enhance the reliability of grid connected to microgrid,a synchronous control strategy is proposed based on the microgrid under the peer to peer control system,aiming at the synchronization problem between microgrid and external power grid.The independent decoupling between active and reactive power,voltage and frequency of microgrid is realized,and the amplitude and phase of grid voltage are output by three-phase phase-locked loop(SPLL),and the synchronization of grid voltage is realized.Through the droop control output integral,the voltage phase of the microgrid interface inverter is obtained,and then the proportional integral(PI)regulator is used to carry out the zero difference control,so as to achieve the active synchronization of amplitude,frequency and phase before the grid connected to the grid.Finally,in the micro grid in MATLAB simulation,comparison without adding active synchronization control strategy and the control strategy of the simulation analysis,the results show that the proposed control strategy is effective and feasible,The synchronization of the main parameters of the grid connected to the microgrid is improved well in the application of the traditional droop control.