Abstract
The goal of this article is to introduce the fundamental notions and concepts of stability analysis for linear and nonlinear systems in the context of electronic power conversion. Power electronic circuits have strong nonlinear behavior in their essence; often we need to linearize them to understand their properties and study their stability with the applied control laws. We present different concepts of stability (internal, input-output, Lyapunov-based), observability and controllability, as well as practical tests to check these properties. We then apply these tests in the context of a single power converter example, a DC/DC boost converter. © 2023 Elsevier Inc. All rights reserved.

Abstract
Switched reluctance machines (SRM) are simple, robust and fault tolerant machines, usually operating under strong nonlinear characteristics. Hence, SRM modeling is a most demanding task, in particular core losses. Non-sinusoidal flux density waveforms in different stator and rotor core sections, in addition to lamination non-uniform distribution are challenging phenomena to be addressed. This is still an ongoing research field. The purpose of this paper is to develop a comparative analysis between a linear and non-linear simulation model for core loss distribution in a three-phase 6/4 SRM. Five different steady-state operation modes will be addressed.

Abstract

Abstract
Protection and control systems represent an essential part of distribution networks by ensuring the physical integrity of components and by improving system reliability. Protection devices isolate a portion of the network affected by a fault, while control devices reduce the number of de-energized loads by transferring loads to neighboring feeders. The integration of distributed generation has the potential to enhance the continuity of energy services through islanding operation during outage conditions. In this context, this study presents a multi-objective optimization approach for sizing and allocating protection and control devices in distribution networks with microgrids supplied by renewable energy sources. Reclosers, fuses, remote-controlled switches, and directional relays are considered in the formulation. Demand and generation uncertainties define the islanding operation and the load transfer possibilities. A non-dominated sorting genetic algorithm is applied in the solution of the allocation problem considering two conflicting objectives: cost of energy not supplied and equipment cost. The compromise programming is then performed to achieve the best solution from the Pareto front. The results show interesting setups for the protection system and viability of islanding operation.

Abstract
Modern power grids have high levels of distributed energy resources, automation, and inherent flexibility. Those characteristics have been proven to be favorable from an environmental, social and economic perspective. Despite the increased versatility, modern grids are becoming more vulnerable to high-impact low-probability (HILP) threats, particularly for the distribution networks. On one hand, this is due to the increasing frequency and severity of weather events and natural disasters. On the other hand, it is aggravated by the increased complexity of smart grids. Resilience is broadly defined as the capability of a system to mitigate the effects of and recover from HILP events, which is often confused with reliability that is concerned with low-impact high-probability (LIHP) ones. In this paper, a distribution system in Portugal is simulated to showcase how the utilization of flexibility and mobile energy resources (MERs) should be considered differently relative to HILP vs LIHP threats.

Abstract
In this paper, a multi-temporal optimal power flow (OPF) model for radial networks is proposed. The mathematical problem formulation is presented as a mixedinteger quadratically constrained programming (MIQCP) problem. The main core of the developed OPF problem is benefiting from the second-order conic programming (SOCP) approach while the quadratic constraints of the power flow equations have been efficiently handled. In the developed model, the dynamic behaviour of the electrical energy storage (EES) has been addressed for the day-ahead operation problem. In addition, the developed model is tested and verified for both normal and contingent events and the obtained results are satisfactory in terms of feasibility and optimality. In the islanded operation, a grid-forming unit is the main responsible for maintaining the voltage reference while other units behave as slave. The model is tested on the modified IEEE 33-bus network to verify the performance of the developed tool.