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Towards the green transition of modern power systems, a massive deployment of distributed energy resources (DERs) based on renewable sources is required. These DERs are grid integrated through power electronics converters which reduce the commitment of synchronous generators and as a result, the overall inertia of the system. Maintaining the frequency stability in such low-inertia power systems is a crucial aspect for the system operators; therefore, local control schemes are integrated with conventional generators and DERs to ensure fast reaction in case of frequency disturbances so as to preserve system stability. Existing practices for maintaining the frequency stability rely on the response of a local governor controller integrated with the synchronous generators. Some new approaches introduce frequency support services by DERs, by considering the droop control and virtual inertia concept within the inverter local controller. In another approach, wide area control schemes can also be utilized to further enhance the system stability. Such a wide area control scheme is introduced in this work to coordinate the operation of DERs through 5G communication for enabling fast frequency support services. Due to the fast dynamics of a power system, a reliable and high-speed communication is particularly important for the deployment of the proposed method. Therefore, an experimental hardware in the loop setup has been developed to investigate how the communication performance can affect the stability of the power system. Moreover, a benchmarking is implemented to evaluate the frequency stability when local controllers are providing support and when the proposed wide area controller is applied under a different communication infrastructure. Experimental results demonstrate that when a reliable 5G network is used, then a significant stability improvement can be achieved by the proposed wide area controller.

The fast deployment of the Phasor Measurement Units (PMUs), especially in the transmission level of the power systems, enables the development of wide area monitoring, protection and control (WAMPC) applications that enhance the situational awareness of the power system operator as well as the stability of the power system. Such applications are dependent on the communication network that supports the transfer of the PMU measurements to a central monitoring application or to a local protection application (situated in a substation). It is therefore of paramount importance to ensure the transfer of measurements with the least delay, while at the same time to ensure the integrity of the PMU measurements. In this work, the impact of using a wireless communication network for transferring the PMU measurements to the WAMPC applications is examined and the advantage of the 5G communication network over 4G and 3G in such real-time monitoring and control applications is demonstrated.

Smart5Grid exploits the robustness and flexibility enabled by the 5-th generation (5G) mobile network technology to contribute an open and adaptable platform for reliable testing, validation, and operation of Network Applications (NetApps), addressing the challenges of the Renewable Energy Sources (RES) production and those of the operation of the active power distribution ecosystem, in particular. Smart5Grid aims to support current energy sector and future smart grid stakeholders through the adaptation of 5G networks and the support of the respective NetApps that will be developed and validated on real power grid facilities. Smart5Grid intends to provide a more secure, flexible, efficient, scalable and real-time communication framework for modern smart grids. Through remote inspection and control of automatically delimited working areas, the capabilities of the created Smart5Grid 5G platform will facilitate the improvement of working conditions for power grid maintenance crews and inspection workers. In this paper, we presented the methodology of the Smart5Grid project, which will enable remote inspections in high-risk areas and real-time execution by supporting various distribution network applications and providing accurate results and information on the operational condition of power grid assets via augmented reality. If maintenance work is undertaken, real-time control will be enabled to support working procedures remotely and automatically, without putting employees in potentially harmful conditions.

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This paper aims at assessing the amount of intergenerational social mobility experienced by migrants in Europe and the effects of immigration on European countries’ overall intergenerational mobility. In line with existing studies, we formulate a micro- and a macro-level hypothesis: 1. Immigrants are over-represented among the downwardly mobile, especially if from Central-Eastern Europe and non-EU countries; 2. Immigration enhances intergenerational social mobility rates in receiving societies. The micro hypothesis assumes that migrants downgrade their occupational standing in the receiving society in return for higher earnings. The macro hypothesis is predicated on the fact that newly arriving workers from abroad tend to fill employment slots at the bottom of the occupational pyramid and thus ‘push’ nationals up. A third hypothesis posits that the impact of downward mobility is subjectively less severe among migrants. These hypotheses are tested using six pooled waves of ESS (2002-2012) which include social mobility data as well as information on the migrant status of respondents. We use both ISEI and EGP class schema to model intergenerational social mobility. The analyses converge as regards the micro-hypothesis, but diverge about the overall effect of migration rates on intergenerational mobility, even when factoring in the educational composition and skill complementarity of the immigrant workforce. The hypothesis on the impact of downward mobility on migrants’ life satisfaction is also not supported by evidence.

Microgrids are about to change the architecture and the operation principles of the future power systems towards smartness and resiliency. Power electronics technologies are key enablers for novel solutions. In this paper we analyze the benefits of a “microgrid by design” architecture (MDA), using a solid-state transformer (SST) as a low-voltage grid-former and inverter-based generation only. In this context, the microgrid stability is maintained with the help of “electrostatic energy inertia” that can be provided by the capacitor connected to the DC busbar behind the SST inverter topology. This happens in a natural way, alike the mechanical inertia in power systems with synchronous machines, however without depending on frequency and without the need of a rotational inertia. This type of microgrid always operates (both fully connected to the main grid or in islanding mode) with all the necessary mechanisms needed to maintain the microgrid stable—no matter of the perturbations in the upstream of the point of common coupling (PCC). In the case of microgrids with inverter-based generation only (including the energy storage systems), there is no mechanical inertia and different stability mechanisms need to be applied compared to the stability principle of the classical power systems. Our proposed mechanism differentiates from the recently proposed stability assessments of microgrids based on virtual synchronous generators from the control theory perspective. This paper is a continuation of our previous work where the MDA was first introduced. The use-cases and scenarios are based on realistic and yet reasonable complexities, by coupling the disturbance magnitude with the voltage stability limit in power grids. The paper finds meaningful disturbances to test the electrostatic energy inertia at the boundaries of grid stability, as guidance to understand the range of voltage variation for extreme conditions. The results show that in microgrids with inverter-based generation only and passive loads (RLC type) the operation is no longer frequency dependent. The energy of the DC busbar capacitor as electrostatic energy inertia of the MDA has a role similar to that of the rotational machines in classical grids in terms of maintaining dynamic stability, however impacting two different types of stability.

Solid State Transformers (SST) may become, in the near future, key technological enablers for decentralized energy supply systems. They have the potential to unleash new technologies and operation strategies of microgrids and prosumers to move faster towards a low carbon-based economy. This work proposes a paradigm change in the hierarchically and distributed operated power systems where SSTs are used to asynchronously connect the many small low voltage (LV) distribution networks, such as clusters of prosumers or LV microgrids, to the bulk power system. The need for asynchronously coupled microgrids requires a design that allows the LV system to operate independently from the bulk grid and to rely on its own control systems. The purpose of this new approach is to achieve immune and resilient by design configurations that allow maximizing the integration of Local Renewable Energy Resources (L-RES). The paper analyses from the stability point of view, through simplified numerical simulations, the way in which SST-interconnected microgrids can become immune to disturbances that occur in the bulk power system and how sudden changes in the microgrid can damp out at the Point of Common Coupling (PCC), thus achieving better reliability and predictability in both systems and enabling strong and healthy distributed energy storage systems (DESSs). Moreover, it is shown that in a fully inverter-based microgrid there is no need for mechanical or synthetic inertia to stabilize the microgrid during power unbalances. This happens because the electrostatic energy stored in the capacitors connected behind the SST inverter can be used for a brief time interval, until automation is activated to address the power unbalance for a longer term.

Microgrids present tremendous advantages when it comes to resilience of the distribution sector inpower systems. The DC supply of such small power networks is also appealing due to more and more site based energy harvesting (e.g. RES generation) and electricity storage that is present at building level, as well as more and more domestic and office appliances are DC native loads or DC compatible. There are increasing number of studies with respect to possible architectures and control schemes of such systems, however there is very little work when it comes to power quality (PQ) aspects. The objective of this work is to make useful qualitative and quantitative appreciations into the possible distortions that might appear on the DC bus supplying the loads in a DC microgrid. &nbsp

This work analyzes a number of business models that are exemplified for a lab/campus-scale demonstrator for DC-resilient communities in Bucharest, Romania. The aim of this study is to pave the path that could unlock some of the above mentioned challenges and barriers, and help such networks to flourish in the near future. The analysis is carried out using the Business Model Generation Framework (BMGF), one of the most popular and systematized industry’s state of the art (SoA) tools for developing and creating innovative business models and tools. &nbsp

This work presents the architecture and operational features of a demonstrator developed at the premises of MicroDERLab Research Group at UPB that consists of two interconnected DC low voltage microgrids aiming to serve several research projects that focus on resilient DC LV communities. The architecture of the demonstrator uses a case-driven approach to validate and demonstrate the toolkits to be developed. Concretely, the demonstrator aims to facilitate the experimental assessments of several applications from monitoring and active power management of energy consumption in prosumers’ world, to aggregation of measurement data for modelling, planning, integration, operation and evaluation of distributed Energy Storage Systems. One of the major innovation of the proposed architecture consists in the extension of the functionality of the Unbundled Smart Meter (USM), the so called SMX side that processes all the information coming from the micro-controller of the energy router (ER). Simulated results of a distributed and adaptive energy management system to be tested on this demonstrator are also presented, while briefing a number of use-cases in line with several business models that led us to this design.

Technological developments are pushing for new solutions towards massive integration of renewable-based electricity generation in networks already facing many challenges. The paper presents a new approach for managing the energy transfer towards prosumers making use of a smart management of the local energy storage. The proposed grid design (including storage dimensioning procedure) is based on several operation scenarios in which the prosumer is operating as a “load only” entity (from grid perspective) exhibiting self-resilience and higher energy efficiency. One of the major advantages of this restriction in prosumer operation is the preservation of resilience against changing regulatory environment. This can be realized within a newly proposed Uni-directional Resilient Consumer (UniRCon) architecture. For the proof of concept three use-cases are detailed: (i) PV installations connected behind the meter, (ii) PV and storage available and controllable behind the meter and (iii) the UniRCon architecture. The three use-cases are then compared and assessed for four near-future timelines as starting points for the investment. The numerical simulations show the attractiveness of the UniRCon solution in what concerns both system operation costs and self-resilience. Savings are expressed as opportunity savings arising from difference in tariffs while charging and discharging the storage unit and due to avoidance of curtailment as well as special taxes for connection of PV (depending of regulatory environment). An extension of UniRCon concept is presented also at community scale, with neighbourhood energy exchange inside a cluster envisions energy supply resilience at community scale.

Power quality aspects related to DC stationary microgrids are still on virgin grounds of research. However, they may play an important role both in the design stage and on the microgrid control scheme to be adopted. Currently there is no comprehensive, quantitative and qualitative analysis on which of the power quality parameters are the most stringent constraints to be taken into account. This work is one of the first attempts in defining and quantifying a set of power quality indices for DC stationary microgrids. We relate our analysis on the design aspects of DC/DC power converters that are the most critical elements interfacing sources and loads in a stand-alone low voltage DC microgrid., © 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. I. Ciornei, M. Albu, M. Sanduleac, L. Hadjidemetriou, and E. Kyriakides, "Analytical derivation of PQ indicators compatible with control strategies for DC microgrids," in Proc. IEEE POWERTECH, Manchester, UK, 2017, pp. 1-6. DOI: 10.1109/PTC.2017.7981179 https://www.ieee.org/publications_standards/publications/rights/rights_policies.html

In this article we discuss the concept of European solidarity by distinguishing between transnational and international solidarity. The former refers to support for institutional arrangements aimed at sharing economic risks at the individual level, while the latter entails public agreement to share economic risks at the Member State level. We explore the joint role of cross-border interactions and political attitudes in fostering solidarity ties among Europeans through multilevel modelling based on the 2012 Eurobarometer 77 survey. The article shows that transnational experiences do not have the same effect on different forms of European solidarity, limiting transnational and enhancing international solidarity. Egalitarian individuals are more prone to EU-wide solidarity, with cross-border practices affecting their level of solidarity, while not altering those of the rest of the population. In particular, we find that cross-border practices make egalitarians more inclined to international and less to transnational solidarity.

The last decade marked an exponential increase in photovoltaic (PV) systems installed on the rooftop of domestic residences within Europe and in other developed countries around the world. This situation was basically favored by generous financial schemes such as Feed-in-Tariff. However, such governmental incentives drastically reduced recently or they were already replaced with net-metering schemes which favor a different scenario: increase of self-consumption and decrease of grid back injection. This unstable regulatory environment puts both new and old owners of PV systems under a regulatory financial risk. Battery energy storage systems (BESS) are seen as viable options to overcome such barriers as well as increasing the self-consumption from locally produced energy. Furthermore, formation of resilient communities arranged as clusters of residential microgrids within a small territory is also appealing due to the potential of buying and selling locally produced renewable energy (favored by the smoothing effect load aggregation), reduced power losses within the distribution grid where each prosumer within the cluster is connected, and potential of sharing static or mobile electricity storage installed individually or at community level. We focus this study on the use of storage for increasing self-consumption of PV local production at community level microgrids and develop an optimal scheduling strategy of storage facilities within the cluster over a 24 hour period and one year, respectively. The optimization problem has been framed as a stochastic program with probability weights derived form a k-mean clustering method applied on real PV measured data over one year