Fault models of inverter-interfaced distributed generators: Experimental verification and application to fault analysis

This paper investigates the fault behaviour of inverter-interfaced distributed generators in stand-alone networks. It is shown that the rapid transient response of the inverter control system allows its fault behaviour to be characterised by quasi steady-state equivalent fault models. The choice of inverter control strategy, control reference frame and the method of active current limiting dominate the fault response, especially in case of unbalanced faults. The proposed fault models can be directly incorporated in conventional fault analysis methods of which an example is given for a faulty islanded microgrid. Model validation is carried out by comparing experimental measurements with results of analytical fault analysis using the developed fault models and PSCAD time domain simulations.