Research On Bidirectional Converter Control Strategy In AC/DC Hybrid Microgrid

The AC/DC hybrid microgrid contains two sub nets and combines the advantages of both AC microgrid and DC microgrid,and it can use distributed generations more conveniently and efficiently.The AC/DC hybrid microgrid realizes the energy exchange between the two subnets through the AC/DC bidirectional power converter connecting two bus bus,which is the key to the research of AC/DC hybrid microgrid.The AC/DC bidirectional power converter is the key element that coordinates the power balance of the two subnets in the AC/DC hybrid microgrid.In this paper,in view of the shortcomings that the AC/DC bidirectional power converter cannot control the transmission power in the AC / DC hybrid microgrid,the power balance strategy of the AC/DC bidirectional power converter under bidirectional droop control is studied.The main contents include:The topology of the AC/DC bidirectional power converter is analyzed.Then,established the AC/DC bidirectional converter model in three different coordinate systems,and the filter parameters on both sides of the AC/DC bidirectional power converter are designed.On this basis,the traditional double closed-loop control of the AC/DC bidirectional power converter is studied,and the parameter design of the voltage and current double closed loop is carried out.Finally,a Simulink model is established to verify the feasibility of traditional double closed-loop control of the AC/DC bidirectional converter.The principles of AC droop control and DC droop control are analyzed.Aiming at the problem that the traditional AC/DC bidirectional power converter cannot control the transmission power,a bidirectional droop control strategy is proposed,which normalizes the AC bus frequency value and DC bus voltage value Through calculation and control of the power output power and direction of the AC / DC bidirectional power converter,the AC subnet and the DC subnet can achieve power balance.Finally,the feasibility of the AC/DC bidirectional power converter power control strategy is verified by the MATLAB/Simulink simulation model.Aiming at the operation mode of grid-connected and isolated islands in AC/DC hybrid microgrid,the grid-connected/island mode switching technology of distributed power grid-connected inverter under droop control is studied,and the island of gridconnected inverter is realized by using pre-synchronization.The smooth switching from the mode to the grid-connected mode has analyzed the switching process.Finally,through the RT-Lab real-time simulation platform,a simulation model is built to verify the effectiveness of the control strategy proposed in this paper.