基于阻抗的多分布式电源直流微电网孤岛检测方法

This paper proposes an active islanding method based on impedance measurement for DC microgrids with multiple distributed generators(DGs).In the various presented methods,impedance-based islanding detection faces challenges in DC microgrids with multiple DGs due to the randomness of renewable energy.In the proposed method,the virtual impedance controls are designed to reshape the output impedance of DGs and the input impedance of loads at the detection frequency to ensure a clear distinction between grid-connected conditions and islanding conditions.Thus,the islanding events can be effec-tively detected under conditions that lead to a distinct decrease in system impedance.In this way,the accuracy of islanding detection is improved.Moreover,a dynamic allocation of the role algorithm is proposed to organize the orderly disturbance injection of DGs without communication,avoiding disturbance dilution.In addition,the selection principle of the frequency of disturbance current is proposed by studying the sensitivity of the point of common coupling(PCC)voltage to the disturbance.As a result,the negative influence of multiple DGs,loads,and disturbance dilution can be avoided compared to the existing methods.Finally,the effectiveness of the proposed method has been verified by both simulation and experimental results.