Research On Multi-source Coordinated Control Strategy Of Micro-grid Based On Hierarchical Control

Based on the existing control strategy,this paper proposes the control strategy of energy storage inverter under Smooth switching control strategy of microgrid with improved inverter structure for Micro-grid in different conditions.The master-slave control structure is used to realize the smooth switching of micro-grid system from grid connected condition to isolated network condition.The improved pre synchronization control strategy is adopted to make the micro-grid system switch quickly and reliably from grid connected condition to isolated network condition The simulation model is built to verify the reliability and rationality of the control strategy adopted by the microgrid system under Smooth switching control strategy of microgrid with improved inverter structure.First,when the external network system is in the fault condition,the free and smooth fast switching of microgrid system from grid connected condition to off grid condition is the focus of this paper.When PQ control is used for grid connection and V/F control is used for off grid,the Smooth switching control strategy of microgrid with improved inverter structure is used to eliminate the sudden change of inverter output voltage amplitude,so as to ensure that the system can establish a new AC voltage amplitude and switch freely and smoothly when off grid.Second,when the microgrid system is in the process of pre synchronization,by adjusting its own voltage and frequency to match the phase of the external network,when the two achieve balance,it will be re connected to the grid.Traditional control can make the micro-grid system switch to grid smoothly,but the simulation results show that the process is extremely slow.On the premise of ensuring the power quality of micro-grid system,the Smooth switching control strategy of microgrid with improved inverter structure strategy can quickly realize the free and smooth switching and grid connection of microgrid system.Third,in the microgrid system,the dual loop controller of DC/DC voltage outer loop control and current inner loop control of energy storage inverter can not only ensure the constant DC side voltage,but also control the output power of energy storage inverter to energy storage device.Through the energy storage inverter device,the micro-grid system can switch freely and smoothly under different working conditions.Therefore,it is of great significance to study the smooth handoff control strategy of wind solar hybrid in microgrid system.