Distributed compensation including earth fault compensation for renewable energy resources

This study proposes a 4-phase voltage-source inverter replacing conventional 3-phase inverters, traditionally used in renewable energy resources, which is able to compensate a fault current, when a single-phase earth fault of the power grid occurs. The investigated method is able to suppress the earth fault current and recover current symmetry in 3-phase insulated or high-impedance grounded power grids. Proposed compensation is made by the 4-phase voltage-source inverter with earthed 4^th phase, which can operate, under normal operation condition, equally as a traditionally used 3-phase inverter and supply the ac power grid from the renewable resource. The single-phase earth fault in the power grid is analyzed in the paper. Both simulations and experiments were performed on a mathematical model and on a designed laboratory prototype, respectively, in order to verify the proposed compensation method.