Several sources of flexibility in transmission and, especially, distribution networks are being unlocked by advances in information and communication technologies, aggregators, and new flexibility markets. However, maximizing benefits for both transmission and distribution system operators in a coordinated way requires new algorithms, modeling tools, and modernization of regulatory frameworks. Such approaches must account for uncertainties, the physical and operational constraints of flexibility providers and the grid itself, constraints on information exchange, and scalability, including computational requirements and time constraints. Given the diverse contexts and jurisdictions around the world, there is no single recipe for achieving coordination, but important trends and shared challenges are emerging. This paper surveys the complexities of coordination from technical, market, and technological perspectives, and outlines current practices, proposed approaches, and future research directions to effectively manage, coordinate, model, and leverage flexibility across voltage levels.
The increasing penetration of distributed energy resources (DERs), together with the growing participation of end users, is reshaping the operation of modern distribution networks. In this context, demand response (DR) can provide valuable flexibility to improve system operation, but the large number of small-scale residential loads creates challenges related to scalability, data exchange, privacy, and coordination. Distributed Energy Resource Management Systems (DERMS) offer a promising framework for managing DER integration. However, residential DR is often only implicitly represented and lacks explicit aggregation, disaggregation, and coordination mechanisms. This paper proposes a hierarchical DERMS framework that explicitly integrates residential DR through an aggregation and disaggregation architecture. The proposed approach represents large populations of residential DR participants using compact aggregated flexibility models, thereby reducing the upstream optimization dimension and limiting the exchange of individual customer-level data. A Utility-DERMS scheduling model is combined with a machine-learning-guided Sequential Adjustment Method (SAM) to restore voltage feasibility. The framework is validated on the IEEE 123-node test system under stressed loading, multi-period DR scheduling, and uncertainty-based scenarios. Simulation results demonstrate the effectiveness of the proposed DERMS framework in reducing upstream DR representation and data exchange while achieving voltage-feasible operation, fewer SAM iterations, and effective coordination of DR load shifting and rebound behavior. Benchmarking against centralized OPF and non-aggregated implementations further confirms that the proposed framework provides a practical balance between scalability, privacy-conscious coordination, computational tractability, and voltage-secure operation.
Abstract Reinforced concrete (RC) infrastructure exposed to marine environments and deicing salts suffers from premature deterioration due to chloride-induced corrosion, while existing strengthening systems often provide limited protection once cracking develops. This study investigates chloride transport in an innovative thin strengthening system based on an ultrahigh-performance fabric-reinforced cementitious matrix (UHP-FRCM), incorporating polyparaphenylene benzo-bisthiazole and carbon meshes embedded in a UHP matrix, under coupled mechanical loading and aggressive exposure conditions. Concrete disks and prisms were tested using rapid the chloride migration test, including tests under sustained flexural loading. Digital image correlation was used to quantify crack development and relate crack width to chloride transport. UHP-FRCM systems significantly improved durability compared to commercial systems, reducing apparent diffusion coefficients by up to 90% in uncracked conditions and limiting chloride ingress by up to 80% under loading, with penetration depths reduced to approximately 35 mm. Hybrid matrices combining steel and ultrahigh-molecular-weight polyethylene fibers provided the best performance by controlling crack width and disrupting transport pathways. A clear exponential relationship between crack width and chloride diffusion was observed. Service-life analysis based on apparent diffusion coefficients from accelerated tests indicates that UHP-FRCM systems can increase the predicted time to corrosion initiation at a 50-mm concrete cover depth by approximately 2.5–3.0 times compared with commercial FRCM systems, depending on the applied loading level. The findings demonstrate the potential of UHP-FRCM systems for crack-controlled durability design in chloride-exposed reinforced concrete structures.
This paper addresses the integration of the vehicle routing and three-dimensional packing problems, commonly referred to as the Three-Dimensional Loading Capacitated Vehicle Routing Problem (3L-CVRP). Combining these two classical problems is of significant practical relevance, as the efficiency of load allocation directly impacts the effectiveness of delivery routes. Among the various possible variants, this study focuses on the 3L-CVRP with time windows and considers all feasible orientations of the boxes within the containers. Two mathematical formulations are presented, one with and another without an explicit vehicle index in the routing decision variables. Preprocessing techniques are applied to reduce model complexity and enhance computational efficiency. To solve larger instances, a logic-based Benders decomposition method is also proposed. The performance of the mathematical models and decomposition strategies is assessed through computational experiments using multiple benchmark datasets. The results show the competitiveness of the proposed approaches, which found optimal solutions in 46 out of 124 experiments, 13 of which represent the first proven optimal solutions reported in the literature. Moreover, the proposed methods obtained 33 new best-known solutions on classical and widely studied benchmark sets.
In finite dimensions, every doubly stochastic matrix has the ℓp-operator norm equal to 1 for all 1≤p≤∞. However, in the infinite-dimensional setting, this property may fail since the norm can be strictly smaller than 1 when 1<p<∞. In this paper, a complete characterization of infinite doubly stochastic matrices for which the norm remains equal to 1 is obtained. More precisely, for 1<p<∞, it is shown that‖D‖ℓp(I)→ℓp(I)=1⇔Θ(D∗D)=1, where Θ measures the maximal average mass of a finite square submatrix. Thus, the norm is equal to 1 precisely when the matrix contains arbitrarily large finite regions in which it behaves almost like a finite doubly stochastic matrix. The proof uses a Cheeger-type argument, highlighting a natural connection with ideas from spectral graph theory.
