Research On The Flexible Grid-connected Interface Of Microgrid And Its Control Strategy

With the development of new era technology and the acceleration of electrification process,the application of electric energy is more extensive,and electric energy has become one of the most widely used energy.In order to better realize the development and utilization of new renewable energy,some scholars put forward the concept of microgrid.At the same time,the research on Microgrid by experts is more and more extensive.Microgrid has two operation modes: grid connected and off grid.This paper simplifies the control mode of two mode switching and improves the interface design to make the system more stable.Most of the distributed generation modules in microgrid are renewable energy generation modules,which echo the theme of green environmental protection in the new era.However,renewable energy generation is also accompanied by many problems,such as generation instability and volatility,and more difficult to predict.In order to connect the microgrid with the distribution network,it is necessary to solve the serious problem that the power fluctuation of the microgrid affects the power fluctuation of the distribution network,so as to avoid the fluctuation of bus voltage,current and frequency,and further affect the stability of the large power grid.In order to reduce the threat and impact of microgrid connected with large power grid.This paper focuses on the interface and control strategy of microgrid in parallel with large power grid.In this paper,a flexible grid connection interface of microgrid is proposed,which can stabilize the power fluctuation of microgrid and simplify the grid connection control.The interface is based on back-to-back converter,and the DC side is connected with hybrid energy storage device.On the one hand,the hybrid energy storage system can be supported by storage battery when the microgrid is off grid and the power generation is insufficient,on the other hand,it can be controlled by super capacitor according to the distributed generation module of microgrid Due to the high density and fast response of super capacitor in hybrid energy storage system,it can provide enough capacity support and effectively extend the battery life.DC voltage control is used in the distribution grid side converter,and V / F control is used in the microgrid side converter.Due to the existence of hybrid energy storage system,stable voltage amplitude and frequency can be provided to the microgrid side load regardless of grid connection and off grid,so as to maintain the stable operation of the microgrid system.Finally,the simulation model of flexible grid connection interface of microgrid is built on matlabgsimulink platform,and the experiments are carried out in two modes of grid connection and off grid.The simulation results verify the feasibility of the simplified mode switching,and verify that the interface model can effectively stabilize the power fluctuation of microgrid through DC voltage follow-up control,maintain the stable operation of distribution network,and enable the distribution network side to maintain the operation with unit power factor.