DC Current-controlled Transductor for Fault Current Limitation in Utility-interfaced PV Systems

Although single-stage grid-tied PV topologies are more efficient, easier to implement and lower in cost than two-stage ones, they confront problems in limiting high grid-fault currents. This is related to the fact that they involve a single inverter to perform all grid-interface functions including maximum power point tracking (MPPT), DC voltage regulation, and grid current control. This mandates fault current limiting approaches which don’t impose further complexity on the inverter control. Hence, in this paper, a DC-current controlled transductor (DCT) is proposed acting as a fault current limiter. The DC flux of its core is controlled between a zero and maximum value to vary its impedance between a minimum value during utility-normal operation and a maximum value during fault. This protects the inverter against failure or tripping, thus enhancing system reliability and efficiency. Finally, a 1. 6kW single-phase single-staged grid-connected PV system is investigated during normal and abnormal grid-operation and simulation results verified the proposed transductor effectiveness in limiting fault currents.