Simultaneous Implementation of LVRT Capability and Anti-Islanding Detection in Three-Phase Inverters Connected to Low-Voltage Grids

In the future, the provision of ancillary services in low-voltage grids will become more and more important. Low-voltage ride-through capability has been a requirement in medium- and high-voltage grids but will become mandatory even in low-voltage grids. There may be conflicts with existing requirements such as anti-islanding detection. This paper proposes a method that allows for both low-voltage ride-through capability and anti-islanding protection to be implemented simultaneously in three-phase inverters connected to low-voltage grids. This method uses constant voltage and frequency monitoring and reacts according to the relevant specific requirements. With the proposed method, inverters can contribute to system stability without the risk of unintentional islanding operation. The implementation of low-voltage ride-through capability is shown to even facilitate the detection of islanded grids. To prove the merit of this proposal, a model for a three-phase inverter is developed, which incorporates the proposed method and is successfully tested both in simulation and in experiments in the laboratory.