Research On Microgrid Grid-connected And Island Operation Mode Switching

In order to solve the problem of energy shortage and clean energy utilization,more and more distributed power sources have been developed rapidly,such as the application of photovoltaic power generation and wind power generation technology,but these distributed power sources have the uncertainty of output in operation,and Microgrid can solve these problems better.With the continuous improvement of the micro grid control strategy,for the island and grid connected operation modes,it has basically been able to achieve stable control.However,when the micro grid is switched between grid connected and island operation modes,it is easy prone to shock and long transition time,which affects the operation of the micro grid.Therefore,it is necessary to study the the micro-grid and off-grid switching.Firstly,based on the development of microgrid,the paper designs the model of microgrid inverter based on master-slave control,Study the control performance of inverter.During grid connected operation,Considering the influence factors of three-phase voltage imbalance,the output current will be unstable.Therefore,the original controller is improved,and the voltage feed-forward detection and compensation link is added on the basis of the original control to solve the problem of output instability;When the island is isolated,the common droop control methods are analyzed and summarized.An improved droop control strategy is adopted,and the improved droop control strategy is variable coefficient droop control strategy.The droop coefficient will change with the change of output power,so as to solve the problem of poor dynamic performance of traditional droop control,so as to make the operation of microgrid more stable.Secondly,in order to solve all kinds of impact problems caused by dual-mode switching,the key technologies combined with the control model are analyzed.The control strategies proposed in this paper are added to grid connection and islanding respectively,and the stability of the whole micro grid operation is verified by combining the key technologies of mode switching.Finally,in order to verify the effectiveness of the proposed method,a simulation model was built under MATLAB / Simulink environment.The simulation results show that the transition between the two modes is rapid,the adjustment is accurate,and there is no impact,which improves the reliability of power supply,thus verifying the feasibility of the control strategy proposed in this paper.