Fast islanding detection and grid-injected current compensation for distributed generation with synchronous machine

Fast islanding detection methods for inverter-based distributed generation such as photovoltaic system have been well investigated. However, fast islanding detection for distributed synchronous generation is more challenging due to the inherent large system inertia. Existing methods based on sharp frequency and/or voltage change due to sudden power imbalance and system impedance may not be able to ensure highly reliable detection, small non-detected zone, and fast detection. Meanwhile, unbalanced load and harmonics caused by the wide application of power converters would cause power quality issues and complicate the detection of islanding because of distorted waveforms. As a result, a compensator consisting of a diode rectifier and a MOSFET inverter is proposed to fast detect the loss of mains while the power quality of the grid interface could be improved. The effectiveness of the proposed approach has been thoroughly investigated and verified by simulations in EMTDC/PSCAD.