Fuzzy optimization of islanding detection algorithm based on active frequency drift with positive feedback

WU Fang-de， ZHANG Ben-ben， XV Fang
（Key Laboratory of E&M， Ministry of Education & Zhejiang Province， Zhejiang University of Technology，
Hangzhou 310014， China）

Abstract： Anti-islanding protection is mandatory feature for grid-connected inverters. Active frequency drift（AFD） with positive feedback islanding detection method is the most widely used at present. It is difficult to give consideration to non-detection zone and output power quality when chose the algorithm parameter. In order to solve the problem，firstly，the relationship between the algorithm parameter and the above two aspects was analyzed，and then the rang of algorithm parameter was given. Finally，the feedback parameter was adaptively online adjusted based on fuzzy control according to the change of voltage frequency at point of common coupling when grid disconnect.Simulation model for islanding detection based on Simulink/SimPowerSystems was established. Simulation results demonstrate this method not only can have no non-detection zone，but also reduces the output current distortion by 1.49% than the conventional algorithm.
Key words： grid-connected； photovoltaic system； islanding detection； active frequency driftt（AFD）； fuzzy optimization