The Reserch On Active Synchronization Between Microgrid And Electric Power System

Recently, with the growing problem of environmental pollution and energy shortage, more and more attention has been paid on the development and utilization of renewable energy sources by the world. The microgrid provides the reliable power for the local load by combining the multiple distributeted generators, and also shows the advantages of the distributed generation sufficiently. When the microgrid is requested to reconnect to the main grid, the static switch can be closed after the voltage satisfy the standard of reconnection, or there will be a rush current which may impact the steday state of the main grid and even damage the distributed generators or other equipments.In this paper, the microgrid system is composed of a voltage source inverter and a synchronous generator, and an active synchronizing control scheme is proposed aimed at the synchronous problem of the microgrid and the main grid to reduce the rush current. The scheme is based on two layers’ hierarchical control strategy, which includes microgrid central control layer and local control layer. The microgrid central control layer consist of the slip signals detection unit and the active synchronizing adjustment unit. The slip signals detection unit detects the voltages of the main grid and microgrid, and get the slip signals rapidly through simple calculation, and check whether the slip signals satisfy the standard of reconnection; the active synchronizing adjustment unit adjusts the slip signals and sends the regulatory signals to the local controller to adjust the voltage of the microgrid until the slip signals satisfy the standard of reconnection. The local control layer adopts droop control stragety to relieze the parallel operation of the distributed generators and the “peer-to-peer” control. Under the MATLAB/Simulink, the inverter and synchronous generator simulation model is built to verify the active synchronizing control scheme, the results proved the scheme can relieze the synchronization of the main grid and microgrid, and reduce the negative impacts of the rush current.Finally, the open-loop test experiment and the closed-loop experiment are completed at the experimental platform of three-phase inverter. The experimental results are consistent with the theoretical analysis, which proved that the proposed scheme is effective and superiority.