Research On Voltage Unbalance Control Strategy Of Islanding Micro-grid Inverter

From the developed to the developing countries,the overuse of energy has accelerated the global dilemma of the depletion of non-renewable energy sources.In recent years,global energy consumption has been growing at a high speed,among which the excessive combustion of primary energy will produce a large number of greenhouse gases,mainly carbon dioxide,and the damage to the earth's environment cannot be ignored.Under the dual challenges of energy saving and environmental protection,new energy power generation technology has been widely concerned.The traditional centralized power generation method can no longer meet the requirements of environmental protection and energy maximization.As a new distribution mode,microgrid can effectively control the problem of energy dispatching in the system and make renewable energy widely used.Droop control is commonly used in microgrid.One of the advantages of droop control is that which can reasonably realize the problem of power sharing among multiple microsources and better control voltage and frequency stability.In this paper,the output voltage stability of the micro grid inverter in island mode is studied.The droop control can lead to the voltage instability,which leads to the instability of the whole micro grid system.In this paper,the fuzzy PI algorithm is introduced into the traditional droop control,change control coefficient so as to realize prolapse controller when the reasonable distribution of power will not affect the stability of the inverter output voltage at the same time,considering the problem of line impedance for positive sequence current output voltage separation and adding virtual negative impedance loop to improve the voltage quality.Firstly,this paper introduces the development background and definition of microgrid and the development history of fuzzy control.Secondly,it introduces the islanding structure of microgrid,the structure and working principle of inverter,establishes the traditional droop controller,and analyzes the voltage instability caused by the reasonable power distribution when the droop controller is used in the inverter.Then the principle of the fuzzy PI controller is analyzed and the fuzzy PI algorithm is introduced into the droop controller to change the droop controller coefficient,so that the output voltage is stable when the power is distributed reasonably.Finally,the simulation model of the traditional droop controller and the improved droop controller are established by Matlab/Simulink,and the experimental results are compared to verify the effectiveness of the proposed voltage imbalance control strategy.