Research On Power Decoupling And Reactive Power Sharing Control Strategy Of Micro-Grid Inverter

Droop control is one of the main control methods of micro grid system,which has the advantages of no communication connection and realizing “plug and play” of micro source.When droop control is applied to resistive or resistive circuits,power coupling and power imbalance will occur due to line impedance mismatch,and then affects the stability of system Therefore,this paper mainly studies the output power coupling and reactive power sharing of micro-sources in low-voltage micro-grids.The main contents are as follows:Firstly,establishing the mathematical model of the micro-grid voltage source three-phase inverter,and expounding the basic principle of the droop control.Analyzing the power coupling characteristics under the condition of pure inductive circuit,pure resistive circuit and complex impedance circuit of the system and analyze the power module,droop control module and the voltage and current double closed-loop control module of the control part.Then,deriving the power expressions and corresponding droop control equations,and the conditions of realizing the equal distribution of reactive power balance of the system.Secondly,in order to realize the power decoupling of the inverter,proposing a power decoupling control strategy based on virtual impedance.Through the virtual complex impedance,regulating the output impedance of the system be inductive.Analyzing the power decoupling progress on nodes after the introduction of virtual impedance At the same time,the virtual complex impedance control method with the impedance ratio is used to suppress the natural voltage offset caused by the introduction of virtual impedance.Through simulation,the results show that the virtual complex impedance can not only realizing the power decoupling function,but also restrain the voltage drop.Finally,in order to improve the precision of reactive power sharing after introducing virtual complex impedance,an adaptive virtual complex impedance control strategy is proposed.Introducing the self-adaptive virtual impedance coefficient to design the virtual complex impedance,and obtaining the impedance coefficient expression under the conditions of reactive power sharing.Then,analyzing and comparing the accuracy of reactive power sharing by the proposed controller and the traditional droop controller.Through simulation,the results show that the proposed adaptive virtual complex impedance control strategy can significantly improve the precision of reactive power sharing.