Microgrid islanding can improve the reliability of distribution networks by enabling load to be supplied even after a fault has occured nearby. The generation and load devices in microgrids are commonly interfaced by power electronics, causing a lack of inertia in the network. When microgrids transition from grid-connected to islanded operation after a fault, fast dynamics occur which have to be evaluated to assess stability during and after the transition. Their stability can be evaluated by time-domain simulations, however detailed and validated models of power electronic loads and distributed energy resources are required. This paper proposes component-based models of different types of power electronic loads, and single and three phase distributed energy resources. The models are validated with a variety of voltage and frequency transient experiments. A case study is performed where a modified version of the Cigre European LV residential network is islanded after a fault occurs. The results of the proposed, constant impedance and exponential load models are compared. The results indicate that the proposed models should be used for accurate analysis of the voltage and frequency stability during microgrid islanding simulations.