Research On Reactive Power Compensation Of Microgrid Based On Improved Droop Control

This paper is mainly based on the traditional droop control,and studies the parallel control strategy of micro-source inverters with different capacities in the micro-grid.Traditional droop control is used as the operation control method of universal parallel inverters.Because it does not require interconnected communication,plug and play,strong margin and flexibility and other advantages are widely used.It can effectively adjust the frequency and voltage of micro-capacitors with different capacities to make the micro-grid operate stably,safely,reliably and efficiently.When micro-grid island operation,due to the characteristics of renewable energy distribution,different types of distributed micro-sources are located in different locations and the distances between micro-sources and local loads are different.By analyzing the mathematical model of the power transmission characteristics of micro-sources using traditional droop control,therefore,it is concluded that due to the deviation of the equivalent line impedance between the micro sources.As a result,the micro-power supply using droop control cannot reasonably distribute the reactive power output by the inverter according to its rated capacity ratio,which results in reactive circulating current between the micro-power supplies,thereby increasing system loss and reducing power quality.In view of the above problems,this paper proposes an improved droop control strategy.The mathematical model of the voltage source inverter is deduced.Based on the mathematical model,a current and voltage double closed-loop control system is designed,and the parameter design method of the voltage and current double closed loop control system is studied.And the parameter design method of voltage and current double closed loop control system is researched.The theoretical analysis of the factors affecting the reactive power circulation of the micro-grid is theoretically performed,and the factors affecting the reactive power circulation are simulated.Then a new improved droop control strategy is introduced,which introduces the reactive power compensation link into the traditional droop control to offset the equivalent line impedance between different micro sources.The introduction of reactive power compensation will cause a deep drop in the system voltage.In order to compensate for the voltage drop caused by the reactive power compensation amount,according to the principle of the system voltage drop,a micro-source-side voltage loss recovery mechanism is added to ensure the system voltage quality.Finally,build a micro-grid Matlab/Simulink simulation model.The simulation results show that the improved droop control strategy can reasonably distribute the reactive load under the condition of different line impedances and sudden changes in load,without affecting the active output of the micro power supply and reducing reactive circulating current,maintaining the system voltage stability.