Exploring Operational Flexibility of Active Distribution Networks with Low Observability

Power electronic interfaced devices progressively enable the increasing provision of flexible operational actions in distribution networks. The feasible flexibility these devices can effectively provide requires estimation and quantification so the network operators can plan operations close to real-time. Existing approaches estimating the distribution network flexibility require the full observability of the system, meaning topological and state knowledge. However, the assumption of full observability is unrealistic and represents a barrier to system operators' adaptation. This paper proposes a definition of the distribution network flexibility problem that considers the limited observability in real-time operation. A critical review and assessment of the most prominent approaches are done based on the proposed definition. This assessment showcases the limitations and benefits of existing approaches for estimating flexibility with low observability. A case study on the CIGRE MV distribution system highlights the drawbacks brought by low observability.Comment: This paper has been accepted to the IEEE Belgrade Powertech 2023. It has 6 pages, 4 figures, and 2 table

A Novel Machine Learning-Based Load-Adaptive Power Supply System for Improved Energy Efficiency in Datacenters

Power Supplies are a key part of the modern Internet and Communications Technologies (ICT) industry. Modern Uninterruptible Power Supply (UPS) systems are modular and as such, consist of several Power Supply Units (PSUs). Even though various PSU designs are used to optimize operation efficiency at specific loading conditions they engender inefficient operation at other loading conditions. In order to optimize the energy efficiency in various loading conditions, this paper proposes a novel power supply multiplexing system engaging different combinations of PSUs which are controlled through machine learning techniques to maximize efficiency depending on the loading conditions. Each PSU combination is given a state number. Due to the vast number of combinations (states) that can occur in such systems and redundancy requirements, machine learning techniques are proposed. It is shown that by using the proposed novel system, an efficiency improvement of over 78% can be achieved in low loading conditions and an average 5.23% in all loading conditions.ISSN:2169-353

Impact of inverter-based generation on islanding detection schemes in distribution networks

One of the most frequently used interface protections for Distributed Generators (DGs) is the Loss of Mains (LoM) protection. It detects the formation of an island at the connection point and disconnects the DG to protect the unit, the system and the personnel. The increased penetration of inverter-interfaced DG, in combination with the decommissioning of synchronous generators, reduces the system inertia and leads to faster changing and larger voltage and frequency deviations. Therefore, modern grid-codes require inverter-based DGs to provide support to the grid by modifying their active and reactive power injection based on local measurements. However, this leads to complex inverter-grid interactions and modifies the islanded system behavior, thus disturbing the operation of LoM protections that rely mainly on local voltage and frequency measurements. In this paper, we propose an improved analytical formulation for estimating the Non-Detection Zone (NDZ) of LoM protection devices in the presence of grid-feeding inverters, as well as novel NDZ approximations for grid-supporting and grid-forming inverter-based services. We verify the analytical results with detailed dynamic simulations and comment on the impact that the new inverter requirements have on the performance of LoM protections

Life Cycle Assessment of concrete manufacturing in small isolated states: the case of Cyprus

Life Cycle Assessment (LCA) is an effective and valuable methodology for identifying the holistic sustainable behaviour of materials and products. It is also useful in analysing the impact a structure has over the course of its life cycle. Currently, there is no sufficient knowhow regarding the life cycle performance of building materials used in the case of small isolated states. This study focuses on the LCA of the production of concrete for the investigation of its environmental impact in isolated island states, using the case of Cyprus as an example. Four different scenarios for the production of 1 tonne of concrete are examined: (i) manufacturing of concrete by transporting raw materials from different locations around the island, (ii) manufacturing of concrete using alternative energy resources, (iii) manufacturing of concrete with reduced transportation needs, and (iv) on-site manufacturing of concrete. The results, in terms of environmental impacts of concrete produced, indicated that the use of renewable electricity instead of fossil-fuelled electricity in isolated states can drastically improve the environmental performance of the end product. Also, the minimisation of transportation distances and the use of locally available resources can also affect, to a degree, the environmental impact of concrete production. Abbreviations: AP: Acidification Potential; CRC: Completely Recyclable Concrete; GWP: Global Warming Potential; HFO: Heavy Fuel Oil; LCA: Life Cycle Assessment; LCI: Life Cycle Inventory; LCIA: Life Cycle Impact Assessment; MPA: Mineral Products Association; ODP: Ozone Depletion Potential; POCP: Photochemical Ozone Creation Potential; PV: Photovoltaic