Improved Virtual Synchronous Machine with Grid Impedance Estimator for Islanding Detection

The Virtual Synchronous Machine (VSM) concept enables grid-support functionalities in grid-tied converters. Like conventional inverters, VSM-driven inverters must ensure anti-islanding protection. However, dedicated methods for VSM-driven inverters are lacking in the literature. Therefore, this work proposes an Estimation Evaluation Algorithm integrated into a VSM-based grid impedance estimator. The presented algorithm triggers the estimator whenever a potential islanding condition is detected. When a large variation in grid impedance is measured, the VSM-driven inverter detects islanding and trips accordingly, complying with international standards for equipment connecting renewable energy sources (RESs) and energy storage systems (ESSs) to the grid. Experimental tests are conducted on an industrial 8 kVA grid-tied inverter according to the anti-islanding specifications of international standards, thus validating the proposed solution.