A Control Strategy for Parallel Operation of Multi-Inverters in Micro-Grid

The application of the traditional droop control method will lead to increased circulation and uneven distribution among paralleled power inverters in the micro-grid system with multiple inverters,due to the difference between the output impedance and the line impedance of the inverter.In this paper,firstly,the traditional droop control method was introduced,the power distribution was analyzed when the output impedance of the inverter was resistiveand the inherent limitations of the conventional droop control scheme were indicated.Then the resistive virtual impedance was introduced and the concrete addition position of the virtual impedance was given in order to meet the demands of precise power distribution and equivalent resistive output impedance,which were the prerequisites for correctly using the traditional droop control method.The addition of the voltage feedback in the traditional droop control could solve the voltage deviation.Finally,simulation results demonstrated that the control strategy was correct and effective.