Study on the over-voltage and over-current of grid-connected inverters in non-fault conditions

Over-voltage and over-current of grid-connected inverters not only affect their grid-connected or isolated operation modes directly, but also relate to the safety of their components. Over-voltage and over-current of grid-connected inverters in non-fault conditions are investigated in this paper. The over-voltage on dc-link and the filter capacitor as well the over-current caused by inrush current of isolation transformer are studied in detail. Simultaneously, their physical mechanisms and mathematical models are established. Furthermore, some response strategies are presented to overcome these over-voltage and over-current processes. At last, based on a typical grid-connected inverter topology, some simulation results are achieved using PSIM and PSCAD/EMTDC. In addition, a prototype is set up and some experimental outcomes are presented. The simulation results and experimental tests have verified the validity and effectiveness of the proposed models and methods.