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Decarbonization and decentralization are major trends in the transformation of conventional power systems. The increase of the penetration of renewable electricity generation into generation mix contributes to the reduction of greenhouse gas emissions. At the same time, one has to ensure that the reliability and operational flexibility as measured by respective metrics meet specified standards. This calls for a solution of a set of engineering, economic, and institutional problems, the list of which depends on the features specific to countries and regions in question. This is due to differences in the requirements established by technical regulations, the rules governing wholesale and retail electricity and capacity markets, the mix of electricity consumption, as well as the principles underpinning the management of capacity expansion and operation of power systems. The purpose of this article is to provide the rationale for the feasibility and efficacy of integrating hybrid community mini-grids into power systems. The balance of community mini-grids in terms of power and capacity allows them to operate both in the grid-connected and islanded modes without disrupting power supply to consumers. The main sources of electricity in hybrid community mini-grids are distributed generation (DG) facilities, including those based on renewables as well as energy storage systems (ESS). Load dispatching of community mini-grids is performed by an intelligent automatic control system (ACS) governed by decentralized algorithms, which provides coordinated operation of emergency control and power flow automatics. Integration of community mini-grids into power systems can be accomplished through several transmission lines that form an interconnection. The controlled flow of power through such an interconnection allows for significant system-wide technical and economic effects. We propose a technique to provide the rationale for the efficacy of creating community mini-grids. The technique is based on calculations of reliability metrics. The integration of hybrid community mini-grids into power systems makes it possible to increase the availability and uninterrupted supply of electricity to consumers, as well as the lifetime of power grid equipment.

The article presents the results of research aimed at developing digital models for power flow analysis of railway power supply systems (RPSS) equipped with distributed generation (DG) units based on renewable energy sources. We employed the technique of modeling in the phase reference frame, which has the following features: system-wide consistency, which enables modeling power flows in a way that takes into account the properties and characteristics of a complex RPSS and the feeding power system; versatility, which allows for modeling of traction networks of various designs; comprehensiveness, which consists in the possibility of power flow analysis of normal, emergency, and special states of a RPSS, such as those occurring during de-icing of overhead contact system wires. Three groups of models have been developed. The first one was designed for power flow analysis RPSSs with DG units based on synchronous generators driven by mini-HPP turbines. It is also possible to apply this model in the case of inverter generation that uses photovoltaic panels. The second group of models provided simulation of RPSS power flows with induction generators. The third group enabled power flow analysis in the case where there are three-phase generators connected to a single-phase traction network by means of Steinmetz converters. Active harmonic conditioners and controlled reactive power sources were used to reduce the negative impact of inferior power quality on voltage deviations and harmonic distortion. Simulation results produced by the software package Fazonord showed that the following positive effects can be obtained on the basis of the use of RES-based DG units: reduced costs of power supply; reduced imbalance on the buses of district windings of traction substations, stabilization of voltage levels on bow collectors of electric locomotives.