Active Frequency Drift Islanding Detection Method for Photovoltaic Grid-Connected Power Generation Systems

The Active Frequency Drift (AFD) islanding detection method is a critical technology for identifying unintentional islanding phenomena in grid-connected photovoltaic systems, ensuring system stability and operational safety. This technique utilizes the principle of active frequency drift by manipulating power electronic devices in the control system. AFD algorithms typically involve injecting a controlled phase shift or frequency perturbation into the inverter's output current, which causes voltage frequency deviations at the Point of Common Coupling (PCC) when grid disconnection occurs. Implementation often requires embedded programming in digital signal processors (DSPs) to dynamically adjust switching frequencies based on grid voltage zero-crossing detection. The method can be integrated with other detection techniques (e.g., voltage/frequency relays) through logic circuits or software-based decision-making modules to enhance detection reliability. Therefore, applying AFD technology during the construction and operation of photovoltaic grid-connected systems significantly safeguards system stability and security. Continuous technological advancements are further refining AFD through improved perturbation strategies and harmonic compensation algorithms, providing robust technical support for future developments in grid-connected photovoltaic systems.