Research On Control Strategy And Stability Of AC/DC Hybrid Microgrid

As more and more domestic clean energy is connected to the microgrid,the advantages of microgrid,such as strong flexibility and high energy utilization,are more prominent,making it an important part of building smart grid.Compared with the single AC or DC microgrid,the AC/DC hybrid microgrid can transmit power to each other,which improves the stability of the microgrid operation.However,with the large number of applications of microgrids and the increasing grid-connected capacity,the grid inertia,power flow,voltage amplitude and frequency are affected by load changes and line impedance.Its power distribution,power quality and stability issues are also worthy of our research and analysis.In this paper,three topologies of hybrid microgrid are studied.Mathematical modeling is conducted for three types of micro power sources,namely wind turbine,photovoltaic,and energy storage,as well as the interlinking converters between the micro power sources and the microgrid.The control strategies of power conversion devices are studied,mainly including PQ control strategy,V/f control strategy,and droop control strategy.By comparing and analyzing the limitations of traditional control strategies,a virtual impedance is added to the line,an adaptive virtual impedance droop control strategy is proposed,which can not only achieve the proportional distribution of system power,but also improve the power quality and stability of the power grid.The effectiveness of using the improved droop control strategy for interlinking converters is verified in Matlab.The AC/DC hybrid microgrid model is built in the ETAP simulation platform,and the transient stability of the power grid under different simulation scenarios is simulated and analyzed.The influence of the converter switching of the micro power supply on the power grid under the droop control strategy and the impact of the load impact or switching on the grid bus are explored.The harmonic analysis of the built simulation example is carried out to explore the influence of the generated harmonics on the microgrid and the main grid.The simulation results can provide a reference for the stable operation of microgrid.