Research On Smooth Switching Of Microgrid Dual Mode Inverter

With the rapid development of human beings,the demand for energy is also increasing,therefore,the energy problem has become more and more prominent and has attracted more and more attention,how to improve the utilization rate of energy is a difficult problem that we need to solve urgently.Microgrid and smart grids have opened the electric revolution,the state has also vigorously supported the development of micro networks,the control of microgrid dual mode inverter is the most important technology for the smooth switching between the two working modes of grid connected and off grid.The main circuit,filter circuit and control strategy of microgrid dual mode inverter are classified according to the different structures,through comparison and analysis of their different performances,a method suitable for the system is selected and its parameters are calculated.In this paper,an improved software phase locked loop method is adopted to solve the voltage impact in the switching process of dual mode inverters,in the grid connected operation mode,it is necessary to analyze and compare the circuit structure and the current control loop,and design its parameters.The control strategy adopts PQ control mode,and the transfer function and control circuit of this method need to be deduced and designed respectively.The grid connected inverter is divided into direct grid connected and load connected grid,and these two possible scenarios are analyzed respectively.After comparing the constant voltage constant frequency control with the droop control,the droop control is more suitable for the system in this paper.And it is necessary to design the double loop vector control system.When the load is relatively high for power supply,two inverters need to be connected in parallel to realize the power supply,however,in this process,the problem of circumfluence will occur.In this paper,virtual impedance is introduced into the control circuit to solve the problem.Finally,in MATLAB/Simulink,the whole system is simulated and analyzed from grid connected off grid/grid connected operation mode,the conclusion can prove that the system can achieve the desired smooth switching effect.