Negative Sequence Current Conpensation And Sharing Strategy For Microgrid With Imbalance Based On Model Predictive Control

The wide application of the microgrid has great significance for the development of new energy resources and environment protection.It not only provides an effective way for the use of the clean energy but also has become an important complement for the traditional power grid.Considering the distributed characteristics of the microgrid and its application,there will often be imbalance states in the microgrids caused by the single-phase loads,which affects the stable operation of the microgrid and brings security risks.How to eliminate the unbalanced state of the microgrid is an important problem in the theory research about the microgrid control.This paper mainly deals with the problems about the unbalanced state of microgrids based on power electronics.Based on the centralized and distributed mathematical model of the microgrid,the symmetrical component method is used for the calculation of positive and negative sequence components in the microgrid.Considering the characteristics of the distributed structure,the parallel distributed model predictive control method based on the neighborhood communication is used to solve the negative sequence current compensation problem of the unbalanced microgrid;By the combination of droop control and model predictive control,this paper studies the instantaneous power calculation in unbalanced microgrid.The instantaneous power is divided into positive sequence component,negative sequence component and the double fundamental oscillation component,which is used to correct the calculation for droop control;Based on the voltage unbalance factor for the traditional power grid,this paper gives the definition of the voltage unbalance factor for the microgrid and an optimization function with a penalty term for the microgrid voltage unbalance factor.Finally,this paper proposes a sharing strategy for the negative sequence current compensation in the unbalanced microgrid.In this paper,the simulation based on Matlab has been carried out to verify the effectiveness of the proposed control method and the sharing strategy.