Research On Control Strategy Of Hybrid Microgrid AC/DC Bidirectional Power Converter

Smart grid is an important way for the development and operation of future power systems.AC-DC microgrid plays an important role as an integral part of the smart grid.Its advantages are: 1)AC-DC microgrid contains AC bus and DC bus,enough to accept various distributed energy sources enable them to support each other's power output to meet the system load demand;2)Reduce the power electronics and other intermediate links,reduce engineering operating costs and engineering operational losses;3)Extend the distributed energy and load connections into the system's selectivity and flexibility,and improve the system's energy conversion efficiency,and power supply reliability.This article focuses on hybrid microgrid AC/DC bidirectional power converter control strategies and other related technologies.Specific research work includes:(1)Aiming at the problems of AC and DC microgrid and the transient impact on the DC bus when distributed energy is connected to the grid,a control strategy for improved droop control is proposed.The improved droop control is applied to the three-level converter and three The low switching loss of the level converter realizes the suppression of the DC bus transient voltage in the AC-DC microgrid operation,ensures the stability of the AC-DC microgrid during dynamic operation,and improves the flexibility of the distributed energy grid connection.Theoretical analysis and simulation verify the effectiveness of the control strategy.(2)A bidirectional converter compensation control strategy is proposed for the transient current and voltage surges caused by the control switching process of AC/DC microgrid on/off operation.The control strategy is based on master-slave control under the microgrid using constant power control and constant voltage/constant frequency control,and proposes compensation algorithms for voltage term and current term.Theoretical analysis and simulation results show that the control strategy effectively maintains the power balance of the AC/DC microgrid and the AC/DC microgrid switching control is seamless and smooth.(3)For the stable commutation of the AC/DC microgrid power electronic interface converter,the mathematical model of the three-phase stationary coordinate system and the two-phase rotating coordinate system of the bidirectional converter is deduced,and the bidirectional converter master is designed.The filter inductance and the filter capacitance of the circuit improve the stability of the AC/DC microgrid interface.The simulation verified the validity and rationality of the filter inductance and filter capacitor parameter design.