An improved droop control method for voltage-source inverter parallel systems considering line impedance differences

Abstract

In this paper, the effect of the line impedance difference between various inverters on power sharing with the traditional droop control method is fully analyzed. It reveals that the line impedance difference causes a significant reactive power error. An improved droop control method to eliminate the reactive power errors caused by the line impedance errors is proposed. In the proposed method, a voltage compensation determined by the actual reactive power error between the local inverter and the average one is added into the local voltage reference based on the CAN communication. Even when the communication is interrupted, the controller will operate with the last value of the average power, which still outperforms the traditional method. The effectiveness of the proposed control method is verified by simulation and experimental results, which show the proposed method possesses the better power sharing performance and dynamic response.