Valid models are of fundamental importance for the research and ??development of next-generation power systems with highly integrated ??renewable energy sources. The models provide the basis for planning, ??optimization, and dynamic control. In this presentation, various ??stages of modeling that are critical for the integration of ?renewables ??are presented. The first stage concerns the planning. The ?planning ??model is based on the outcome of the European Union’s ?project ??eHighway2050. We show how the corridors of the future ?European power ??grid are designed in accordance with the European ?Union’s climate ??objectives. Secondly, a method for the multiscale ?modeling of electric ??power systems to cover the different timescales ?of transients is ??desirable. Instead of using just instantaneous real ?signals to track ??the AC voltages and currents, the latter are ?modeled through analytic ??signals that also comprise orthogonal ?imaginary parts. Thanks to this ??extension, the Fourier spectra of ?the analytic signals can be shifted ??in the frequency domain so that ?they become dynamic phasors. The ??methodology proposed so uses ?analytic signals to bridge the merits of ??instantaneous and phasor ?signals. It thus enables the efficient ??simulation of diverse ?waveforms. Thirdly, a method for the transfer ??function based ?modeling offering an in-depth insight into the systemic ??behavior of ?wind energy conversion systems (WECS) is developed. It ??readily ?supports the design of maximum power point tracking. In sum, ??the ?presentation points to key selected challenges and gives modeling ??solutions needed in the process of transforming the energy system.