The results of research aimed at developing digital models for calculating the operating conditions of railway power supply systems (RPSS) using wind power plants (WPP) and solar power plants are presented. The implementation of the models relies on the methods of phase coordinates, which enable a systems, universal, and comprehensive approach. The systems dimension is achieved by considering all the significant properties of a complex RPSS and a supply network. The versatility is ensured by modeling traction networks, power lines, and transformers of various designs. The comprehensiveness lies in the possibility of calculating the normal, emergency, and special operating conditions in the RPSS. The study highlights a variety of applications of the wind turbines: to power the facilities located in regions with unstable energy supply; to enhance the reliability of power supply to the consumer whose disconnection could lead to serious consequences; to supply energy to relatively low-power facilities. The creation of the calculation model for the RPSS requires the implementation of an algorithm for the interaction of models of individual components and includes the following stages: modeling the rolling stock traffic schedule; developing instantaneous diagrams corresponding to specific time instants and calculating their operating parameters; determining integrated modeling indices. The results obtained using the Fazonord software indicate that the use of wind turbines and solar power plants can bring about the following benefits: cutting down energy supply costs; reducing unbalance on the busbars of traction substations, stabilizing voltage levels on the current collectors of electric locomotives. Digital models have been developed to determine the modes of power supply systems for railways equipped with inverter generation units. A solar power plant based on photovoltaic panels was considered as such an installation. To improve the power quality on 10 kV buses, a phase-controlled reactive power source and an active harmonic conditioner were used. The simulation results showed that by connecting a solar power plant, consumption from the electric power system is reduced and with the mass use of photovoltaic panels, a noticeable technical and economic effect can be obtained. In addition, additional energy sources will improve the reliability of power supply to train traction, as well as signaling and auto-locking facilities that ensure the safety of cargo and passenger transportation processes. The presence of an inverter leads to an increase in harmonic distortion, the values of which can be reduced to acceptable limits based on the use of an active harmonic conditioner. Deviations and asymmetry of voltages on 10 kV buses of traction substations can be reduced on the basis of a phase-controlled reactive power source or a symmetrical device implemented according to the Steinmetz scheme.