Research On Microgrid Grid Connected And Off Grid Switching Control

The development of the global economy has resulted in the depletion of non renewable energy sources.The development and utilization of new energy is the inevitable result of the development.With the development of all countries in the world,the problem of environmental pollution and global warming is becoming more and more serious.In order to solve the contradiction between the development and the quality of life,we must look at the renewable and clean new energy.The research and implementation of distributed generation system has been carried out in many countries.The research of the corresponding microgrid technology has become a hot spot.In this paper,the definition and research of microgrid are analyzed,and the value of microgrid is analyzed.Micro grid can be used as distributed power generation system with grid medium,micro grid technology can effectively solve the contradiction between the two,improve energy efficiency and reduce the environmental pollution bring non renewable energy.In the process of microgrid operation,the switching between the two modes,which is independent and grid connected,gives full play to the advantages of distributed generation and provides uninterrupted power supply for the load.In this paper,the control strategy of grid connected inverter and steady-state operation mode of microgrid inverter is introduced.The PQ control is adopted in the grid connection,and droop control is adopted in the independent operation.Whether the microgrid operates on the grid or off the grid,the load voltage and the voltage in the system are difficult to be identical in both the phase and the numerical value.Therefore,before the operation of the switch,the voltage phase and size of the two must be synchronized.Fault or maintenance power,inverter to droop control,instant disconnect switch grid,microgrid into independent operation mode;the remaining power or power to resume normal work,switch to the PQ inverter control,instantaneous close synchronization switch,micro network into grid connected mode.This is the dual mode switching.In the switching process,due to the factors of micro source types,a switching time will cause the voltage and current impact,this paper proposes an improved droop control strategy based on virtual impedance,the two modes of smooth handover,well completion of reasonable distribution of power.In this paper,the model of grid connected and off grid inverter is built in Matlab/simulink,and two kinds of steady-state operation modes are studied.Based on the first two models,the simulation results show that the switching between the two modes can be carried out smoothly.