1.School of Electrical and Electronic Engineering, Shandong University of Technology, Zibo 255000, China;2.State Grid Quanzhou Power Supply Company, Quanzhou 362100, China;3.East China Branch of State Grid Corporation of China, Shanghai 200002, China

As the penetration rate of distributed generators (DGs) keeps increasing, the islanding effect of multiple DGs is likely to occur in the distribution network. In order to ensure power quality and power safety, the inverter must have the islanding detection function. To solve the problem of dilution effect caused by the opposite direction of injected disturbance of the multi-DG inverter, which would lead to the failure of the traditional islanding detection method, this paper proposes a new islanding detection method based on the fixed frequency control of inverters. This method uses the sinusoidal pulse width modulation technology to control the frequency of the output voltage of one of the inverters to 50 Hz. The islanding frequency is stabilized by the master inverter controlled to the fixed frequency, so that each slave inverter controlled by the phase-locked loop can be restored to the normal operation state to eliminate the dilution effect, and the islanding of multiple DGs is detected. The effectiveness of the method is verified by the simulation on the MATLAB/Simulink.