MATLAB Simulation of Active Islanding Detection Using SFS Algorithm

Islanding detection is a critical technology in distributed generation systems, used to detect whether the grid has disconnected from the main power network, forming an islanded operation state. Active methods operate by injecting specific disturbance signals into the grid and determining the islanding condition based on the system's response. The SFS algorithm (Slip-Mode Frequency Shift method) is a common active islanding detection approach that detects grid disconnection by applying minute frequency shifts to the inverter output frequency. In MATLAB simulation, implementing SFS algorithm for islanding detection typically involves the following steps: First, establish the inverter model for the distributed generation system and configure grid-connected operation conditions. Then integrate the SFS algorithm into the inverter's control strategy by applying a small slip-mode disturbance signal in either the voltage or frequency control loop. When the grid operates normally, the main power network suppresses this disturbance; however, when grid disconnection occurs, the disturbance causes continuous frequency deviation in the inverter, eventually triggering the islanding protection mechanism. The simulation process requires monitoring key indicators such as the inverter's frequency response, voltage waveforms, and islanding detection trigger time to evaluate the effectiveness of the SFS algorithm. This method offers high detection accuracy and rapid response speed, but requires attention to the disturbance signal's impact on power quality. Through simulation analysis under various operating conditions (such as load variations and grid impedance changes), the parameter settings of the SFS algorithm can be further optimized to enhance the reliability of islanding detection.