Abstracts:Transitioning to net-zero emission energy systems is currently on the agenda in various countries to tackle climate change, a global challenge that threatens the lives of future generations. To fully decarbonize energy systems, a radical paradigm shift through deep integration of renewable resources supported by storage technologies is envisaged in multisector energy systems, especially in the electric power sector. As a result, inverter-based resources (IBRs), mainly wind, photovoltaics (PVs), and batteries, will dominate the electric power grids. This transition involves phasing out conventional fossil fuel-based plants and decommissioning associated synchronous machines, the grid’s primary reactive power sources. The ongoing removal of these primary reactive power sources introduces critical operational challenges that could compromise the reliability and stability of the grid. The inverters used for integrating IBRs can deliver diverse crucial ancillary services, particularly reactive power support. However, the potential of IBRs to address reactive power requirements in future decarbonized grids still needs to be fully addressed. The existing literature lacks a comprehensive approach to coordinating and harmonizing the efforts of various stakeholders and drivers to leverage the reactive power capability of IBRs. To bridge this gap, this article thoroughly reviews the reactive power implications for future grids with a considerable share of primary IBRs, comprising distributed and large-scale wind, PV and battery storage plants. This article starts with a summary of the concept, measurement methods, and importance of reactive power for voltage control and how it is managed today utilizing conventional sources. The reactive power transition from current to future grids within the context of the greater energy transition is then discussed by shedding light on its diverse aspects. Afterward, the reactive capability curve of each IBR is derived from the equivalent circuits and equations. Various grid codes and integration requirements of IBRs are then analyzed from a reactive power support viewpoint. Also, the concepts related to reactive power and voltage control comprising control extents, modes, and techniques are elaborated. Finally, recommendations are provided to set the stage for leveraging the capabilities of IBRs to address the reactive power requirements of future grids. The presented material sheds light on the pivotal role of reactive power in future grids and provides a roadmap for policymakers, utilities, and grid operators to manage a seamless transition to a decarbonized grid.

Abstracts:Several interesting problems in multirobot systems can be cast in the framework of distributed optimization. Examples include multirobot task allocation, vehicle routing, target protection, and surveillance. While the theoretical analysis of distributed optimization algorithms has received significant attention, its application to cooperative robotics has not been investigated in detail. In this article, we show how notable scenarios in cooperative robotics can be addressed by suitable distributed optimization setups. Specifically, after a brief introduction on the widely investigated consensus optimization (most suited for data analytics) and on the partition-based setup (matching the graph structure in the optimization), we focus on two distributed settings modeling several scenarios in cooperative robotics, i.e., the so-called constraint-coupled and aggregative optimization frameworks. For each one, we consider use-case applications, and we discuss tailored distributed algorithms with their convergence properties. Then, we revise state-of-the-art toolboxes allowing for the implementation of distributed schemes on real networks of robots without central coordinators. For each use case, we discuss its implementation in these toolboxes and provide simulations and real experiments on networks of heterogeneous robots.

Abstracts:Information technology (IT) security has been, and largely is, based on compartmentalization. To implement compartmentalization, system access privileges are granted depending on the topological location of systems, grouped into perimeters, with network mechanisms (firewalls, VLANs, ...) enforcing isolation between perimeters, thus implicitly trusting systems based on their location. However, history has shown that such trust is misplaced. This has led to the emergence of an alternative paradigm, called zero trust. After contextualizing the history of IT and the emergence of zero trust for securing networks, this article presents a taxonomy of zero trust models and architectures, summarizing the goals and core principles of zero trust. Furthermore, an in-depth description of state-of-the-art technologies and methods, for transforming perimeter-based architectures to mature zero-trust architectures, is provided. This article presents a formalization of zero trust and of optimal zero-trust architectures, to which traditional architectures migrate, as well as a method for positioning migrating architectures relative to this ideal of zero trust, with as purpose of enabling a clearer understanding of the benefits and risks induced by a migration to zero trust. Finally, this article analyses the benefits, and drawbacks, of zero trust, focusing on the security properties granted by zero trust, as well as the vulnerabilities introduced.