Direct current (DC) distribution systems and DC microgrids are becoming a reliable and efficient alternative energy system, compatible with the DC nature of most of the distributed energy resources (DERs), storage devices and loads. The challenging problem of redesigning an autonomous DC-grid system in view of using energy storage devices to balance the power produced and absorbed, by applying simple decentralized controllers on the electronic power interfaces, is investigated in this paper. To this end, a complete nonlinear DC-grid model has been deployed that includes different DC-DERs, two controlled parallel battery branches, and different varying DC loads. Since many loads in modern distribution systems are connected through power converters, both constant power loads and simple resistive loads are considered in parallel. Within this system, suitable cascaded controllers on the DC/DC power converter interfaces to the battery branches are proposed, in a manner that ensures stability and charge sharing between the two branches at the desired ratio. To achieve this task, inner-loop current controllers are combined with outer-loop voltage, droop-based controllers. The proportional-integral (PI) inner-loop current controllers include damping terms and are fully independent from the system parameters. The controller scheme is incorporated into the system model and a globally valid nonlinear stability analysis is conducted; this differs from small-signal linear methods that are valid only for specific systems, usually via eigenvalue investigations. In the present study, under the virtual cost of applying advanced Lyapunov techniques on the entire nonlinear system, a rigorous analysis is formulated to prove stability and convergence to the desired operation, regardless of the particular system characteristics. The theoretical results are evaluated by detailed simulations, with the system performance being very satisfactory.

The European Commission’s Target Model’s main objective is to integrate European electricity markets, leading to a single internal energy market and guaranteeing the instantaneous balance between electricity generation and demand. According to the target model for electricity trading, proposed by the European Network Transmission System Operators for Electricity (ENTSO-E), within each zone, electricity can be traded freely without taking into consideration network limitations. In contrast, for cross-border trading, the exchanges with other market areas are taken into account. Cross-border trade poses a further burden on the interconnection lines, resulting in increasing network congestion, which in turn restricts electricity trading. Thus, calculating the available capacity for trade has a significant ramification on the market. Today, the Available Transfer Capacity (ATC) mechanism dominates cross-border trading, but this methodology may be replaced by the Flow-Based (FB) approach across Europe. This paper investigates both approaches regarding the cross-border congestion management under the market coupling procedure. In our case study, the Southeast Europe (SEE) region is taken into consideration; it consists of both the FB and ATC approach in a five country (Greece, North Macedonia, Bulgaria, Serbia, and Romania) scenario. The purpose of our tests is to perform, compare, and evaluate the effectiveness of each method for the SEE region, while the main findings are the maximization of social welfare, better cross-border trading opportunities, and price convergence via the FB method.

CROSS BOrder management of variable renewable energies and storage units enabling a transnational Wholesale market (CROSSBOW) is an EC-funded project, whose aim is to facilitate the shared use of energy resources by fostering cross-border management of variable renewable energies and storage units, enabling higher penetration of renewable energy sources (RES) whilst reducing network operational costs and improving economic benefits of clean energies and storage units. Towards these goals, CROSSBOW boosts regional cooperation among the system operators in Southeastern Europe (SEE), by deploying nine different tools to support the security coordination center (SCC) of the region. More specifically, the main CROSSBOW product, namely CROSSBOW Regional Operation Centre (CROSSBOW ROC) has proposed and demonstrated a set of functionalities for regional management and operation that enhance the existing regional structures, extending the capabilities of the already established Regional Security Coordinator (RSC) initiatives. Beyond enhancing RSC mandatory functions (including adequacy forecasts, coordinated security analysis, capacity calculations, and outage planning coordination), the ROC-BC product has developed new functions, linking the security considerations of involved TSOs with the operation of the fast-developing and harmonized electricity markets. In this paper, we investigate approaches for coordinated capacity calculation and cross-border trading via market coupling, developed within the ROC-BC product of CROSSBOW. Moreover, we present the final demonstration results as a part of ROC fundamental functionalities. Specifically, both net transfer capacity (NTC) and flow-based (FB) methods are examined and compared within a case study applying to the SEE region. The presented results demonstrate that the FB method exhibits better performance in all examined scenarios, considering three different key performance indicators (KPIs).

The scalability and replicability analysis (SRA) is usually performed for Smart Grid Architecture Model (SGAM) projects to assess the applicability of proposed solutions in various regions, conditions, densities, and sizes. In this framework, the replication and scaling-up roadmap of the Horizon 2020 (H2020) CROSSBOW project encompasses a variety of interesting aspects. This study evaluates CROSSBOW results and their impact under various technical, regulatory, market, and social factors. The relevant methodology follows the literature and is properly adjusted to investigate the level at which the CROSSBOW concepts can be escalated and transferred to different scenarios and regions in an efficient and cost-effective manner. Limitations and challenges regarding scalability and replicability are also illustrated. The results depict the total impact of specific factors on scalability and replicability while useful conclusions are drawn. Lessons learnt from the CROSSBOW are very insightful for the scalability and replicability of other upcoming projects.

Distributed energy resources (DERs), such as prosumers and controllable loads, represent a large and underused reserve of power-system flexibility. Their direct participation in electricity markets is nonetheless blocked by three coupled barriers: individual assets are too small to bid, system operators need a trusted record of what was actually delivered, and prevailing regulation admits flexibility only through aggregators and only toward a single operator. This paper presents DFLEX, a blockchain-anchored marketplace that lets small DERs participate directly, without an obligatory aggregator, in both transmission-level balancing (aFRR and mFRR) and distribution-level congestion management using the same assets. Trust is made structural rather than institutional: each asset holds a W3C Decentralized Identifier and signs its offers, each cleared bundle is committed as a keccak256 Merkle root and a representative set is anchored on-chain for independent verification, and only anonymised, executed activity is exported to a European energy data space. We report one year of simulated-production operation on the Greek island of Skiathos, where 54 enrolled DERs served the national transmission operator (IPTO) and distribution operator (HEDNO). The platform cleared and settled 1365.6 MWh of flexibility across 935,558 settlement records and procured flexibility about 20% below the 2025 balancing-price reference. Modelled net participant revenue ranges from €39 to €591 per year, giving payback within a few years for commercial loads. We assess the market, matching and settlement system at Technology Readiness Level 7 and the on-chain layer at Technology Readiness Level 6, because the latter runs on a test network; the remaining barriers to commercial roll-out are economic and institutional rather than technical.