Abstract
The operation of isolated power systems with 100% converter-based generation requires the integration of battery energy storage systems (BESS) using grid-forming-type power converters. Under these operating conditions, load dynamics influences the network frequency and voltage following large voltage disturbances. In this sense, the inclusion of induction motor (IM) load models is required to be properly considered in BESS power converter sizing. Thus, this paper presents an extensive sensitivity analysis, demonstrating how load modeling affects the BESS power converter capacity when adopting conventional control strategies while aiming to assure the successful recovery of all IM loads following a network fault. Furthermore, this work highlights that generators with converter interfaces can actively contribute to mitigate the negative impacts resulting from IM loads following a network fault. Thereby, two distinct control strategies are proposed to be integrated in the power electronic interfaces of the available converter-based generators: one to be adopted in grid-following converters and another one suitable for grid-forming converters. The proposed control strategies provide an important contribution to consolidating insular grid codes, aiming to achieve operational scenarios accommodating 100% penetration of converter-based generation with a significative percentage of the IM load composition without resorting to a significative increase in BESS power converter sizing.

Abstract
Operating isolated power systems with increasing shares of renewable energy sources requires the integration of battery energy storage systems in order to assure enhanced frequency regulation capabilities. The control mode of power converters interfacing battery energy storage systems to the grid can be based on grid-forming type structures given its superior performance with respect to the mitigation of network frequency disturbances. Nevertheless, in case of network faults, the interactions between existing synchronous units and the grid-forming type converters may adversely affect the global system behavior. Therefore, this paper addresses the study-case of a MW-scale isolated power system with large shares of converter-interfaced renewable generation, operating with both synchronous machines and a grid-forming type power converter. An optimal grid-forming control parameter tuning procedure considering different disturbances is presented, aiming to reduce the associated battery energy storage system power regulating effort following the disturbances. Moreover, it is proposed and discussed the need of a novel rule-based adaptive control solution to switch between different sets of control parameters used in grid-forming type converters depending on the network status following a fault-type disturbance. Extensive numerical simulations performed over different operating scenarios illustrate the performance of the proposed solution.

Abstract
Portugal has developed a national roadmap for hydrogen deployment as a key element of the Portuguese energy transition towards carbon neutrality, with a major contribution towards the electrification of society, generating synergies between the electric and gas systems. Considering the government goals for hydrogen injection within natural gas infrastructures for 2025 and 2030, as long as the indicative trajectories for 2040 and 2050, the authors used the natural gas forecast of the security of supply official report in order to obtain the hydrogen demand and power plant capacity, evaluating the system effort to meet public policy goals. Several alternative scenarios were developed for sensitive analysis, in order to assess the different strategies of hydrogen deployment, considering production from an electrolyzer. Regarding the current Portuguese situation and every scenario outcome, the authors stated that major efforts must be undertaken in order to develop full-scale hydrogen projects in order to meet the national goals.

Abstract
The Smart Transformer (ST) is being envisioned as the possible backbone of future distribution grids given the enhanced controllability it provides. Moreover, the ST offers DC-link connectivity, making it an attractive solution for the deployment of hybrid AC/DC distribution grids which offer important advantages for the deployment of Renewable Energy Sources, Energy Storage Systems (ESSs) and Electric Vehicles. However, compared to traditional low-frequency magnetic transformers, the ST is inherently more vulnerable to fault disturbances which may force the ST to disconnect in order to protect its power electronic converters, posing important challenges to the hybrid AC/DC grid connected to it. This paper proposes a Fault-Ride-Through (FRT) strategy suited for grid-tied ST with no locally available ESS, which exploits a dump-load and the sensitivity of the hybrid AC/DC distribution grid's power to voltage and frequency to provide enhanced control to the ST in order to handle AC-side voltage sags. The proposed FRT strategy can exploit all the hybrid AC/DC distribution grid (including the MV DC sub-network) and existing controllable DER resources, providing FRT against balanced and unbalanced faults in the upstream AC grid. The proposed strategy is demonstrated in this paper through computational simulation.

Abstract
With the expansion of power electronics possibilities for smart homes, new perceptions for power control are emerging, suggesting new possibilities also for smart grids. In this prospect, the solid-state transformer (SST) has a substantial impact to interface smart homes with smart grids, guaranteeing high levels of power quality in both grid (consumed current) and load side (produced voltage). Nevertheless, as advanced contributions, the SST can deal with other possibilities of controllability. In such situation, an analysis of new operation opportunities for the SST into smart homes and smart grid perspectives is offered in this paper. It is discussed the SST principle of operation, with a thorough clarification concerning the proposed control algorithms, as well as an intuitive computational validation contemplating contingencies of operation about power quality effects for the load and grid side. The attained results strengthen the attractiveness of the new operation opportunities for the SST when utilized as interface between homes and smart grids.

Abstract
Future Secondary Substation (SS) design requires a more integrated approach, from the building envelope design, electromechanically equipments to the advanced monitoring and control, taking into account new technical, environmental and economic requirements. The main objective of the project is to develop an integrated solution for the SSS, considering innovative solutions for the building envelope and thermal behavior, power transformer and switching equipment as well as monitoring, protection and control system. This paper presents the specification of future SS developed in Portuguese project NEXTSTEP - Next Distribution SubsTation ImprovEd Platform and describes its mains innovative solution and advanced control functionalities. © 2021 The Institution of Engineering and Technology.