Research On Power Sharing Control Strategy Of Parallel Inverter In Microgrid

Microgrid distributed power supplies need to exchange energy through inverters,and are connected to the AC bus in parallel to operate in the microgrid.However,in the actual multi-inverter parallel system,due to the mismatch between the output impedance and the feeder impedance among the microgrid inverters,it is difficult to reasonably distribute the power according to the inverter capacity using the traditional droop control method.Therefore,this thesis mainly studies the control technology of parallel inverters in microgrid.Aiming at the mismatch between the output impedance and the feeder impedance of the parallel inverters in the microgrid,a power sharing control strategy based on adaptive virtual impedance is proposed in this thesis.This method adds an integration link on the basis of a fixed virtual impedance,combines the improved reactive power demand value to adaptively adjust the distributed power unit,and finally compensates for the feeder impedance mismatch,thereby accurately dividing the output power.This control strategy not only does not need to predict the feeder impedance value in advance,but also does not require the participation of the communication platform,and can be applied in a microgrid with a complex structure.Simulation analysis shows that the proposed adaptive virtual impedance power sharing control strategy has better adaptive ability and power balance performance.Second,during the research process,it was found that when there is a sudden load change in the system,the output current will oscillate violently.At this time,the inverter output power will fluctuate greatly,which easily affects the stability of the system.In response to this problem,an adaptive droop control is proposed in this thesis,which introduces a differential term and a power quadratic term into the traditional droop control,so that the power can be adjusted dynamically following the change of the load.In order to select the improved droop coefficient reasonably,the small signal model is used to analyze the dynamic response performance and stability performance of the system.The simulation results show that when the system has a sudden load change,compared with the proposed adaptive virtual impedance control method,the stability of the system is greatly improved;at the same time,it also exhibits excellent dynamic response performance.In summary,it can be concluded from the research in this article that based on the traditional droop control strategy,in the inverter parallel system,the proposed adaptive virtual impedance control strategy and adaptive droop control strategy can not only achieve Accurate power distribution,higher system stability and better dynamic response.