The share of renewable energy sources interfaced to the bulk power system through power electronic devices is continuously increasing. As a result, the power systems of the future face challenges of stability and reduced inertia and, to maintain the stability of the low-inertia systems, various concepts of grid-forming converter control schemes have been introduced, which enable converters to behave similarly to traditional synchronous machines. As the research in this area is gaining on importance, the sheer amount of papers with models for different kinds of simulations and the complexity of control algorithms may be daunting for newcomers in this field to understand them and to start modeling such devices. Moreover, different control schemes are often erroneously used interchangeably which adds to the confusion. This papers aims to give a clear understanding of the above aspects by explaining details of modeling and initialization of grid-forming converter control schemes for power system fundamental frequency dynamic simulations (root-mean-square or RMS simulations) by using an example of a virtual synchronous machine (VSM). Starting from comparison of traditional systems and systems with a high share of converters and continuing with a functional overview of virtual inertia based converters in modern power systems, a step-by-step initialization of the static and dynamic model is given, focusing on RMS simulations. Finally, selected simulation examples are shown which illustrate main characteristics of virtual synchronous machines and their comparison to real synchronous machines. The presented dynamic model is made freely available in DIgSILENT PowerFactory format.

The article presents a detailed analysis and comparison of proton exchange membrane fuel cell (PEMFC) models with different levels of complexity. Since the full PEMFC model is highly nonlinear and depends on numerous technical parameters that are not usually readily available, this article investigates the adequate complexity level of the PEMFC model for power system dynamic studies. PEMFC models with associated control system are presented and developed in DIgSILENT PowerFactory. The performance of observed models in grid frequency control and low-voltage ride through is demonstrated on a simple single machine infinite bus system as well as on the IEEE 14-bus test system. Results show that the PEMFC can be represented with a simplified model in power system dynamic studies, providing identical power response and satisfying the PEMFC stack boundaries.

The growing presence of distributed energy resources (DERs) requires better orchestration between Transmission System Operators (TSOs) and Distribution System Operators (DSOs) for secure power system operation. While typically studied for reliability, the potential of TSO-DSO energy exchange to improve resilience during extreme events needs more research. Moreover, existing studies focus on leveraging DER flexibility to enhance distribution system resilience. This paper introduces a novel framework that evaluates the impact of DER flexibility on overall system resilience, considering the spatial progression of hazard events across both transmission and distribution networks. The framework encompasses spatiotemporal modeling of hazard scenarios and dynamic analyses to assess contributions of TSO-DSO energy exchange to resilience enhancement, using metrics such as frequency settling time and unserved load. Application of this framework to a 39-node system, representing both transmission and distribution (T&D) network, reveals that DER flexibility can significantly reduce frequency settling time – by up to 47% in high-inertia systems and over 65% in low-inertia systems – highlighting the impact of DERs on the rapid restoration of power balance and the prevention of widespread blackouts. Simultaneously, the unserved load is reduced by approximately 52.49% in high-inertia systems and 39.67% in low-inertia systems.

Contrary to microgrids (MGs) for which grid code or legislative support are lacking in the majority of cases, energy communities (ECs) are one of the cornerstones of the energy transition backed up by the EU’s regulatory framework. The main difference is that, unlike MGs, ECs grow and develop organically through citizen involvement and investments in the existing low-voltage (LV) distribution networks. They are not planned and built from scratch as closed distribution systems that are independent of distribution system operator plans as assumed in the existing literature. An additional benefit of ECs could be the ability to transition into island mode, contributing to the resilience of power networks. To this end, this paper proposes a three-stage framework for analyzing the islanding capabilities of ECs. The framework is utilized to comprehensively assess and compare the islanding capabilities of ECs whose organic development is based upon three potential energy vectors: electricity, gas, and hydrogen. Detailed dynamic simulations clearly show that only fully electrified ECs inherently have adequate islanding capabilities without the need for curtailment or additional investments.