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As the power system becomes more inertia-less, several issues related to stability and control reliability have emerged, provoking desynchronization phenomena, first at the grid-tied inverters and propagating to the entire network. Thus, in order to enhance power system reliability and widen the inverter-based distributed generators (IDGs) withstanding capability under large transients, in this article, an active power compensation scheme, which is partially untangled from the conventional phase-locked loops (PLLs), is proposed. Considering PLLs’ vulnerability due to their high nonlinearity, a more reliable physical magnitude is utilized such as the dc-side current, to improve PLLs’ in an indirect manner, by providing adequate response time to follow the abrupt frequency ramps. This is rendered feasible by introducing a series dc–dc converter at the dc-side, which provides the unique ability to mitigate dc current deviations, allowing the regulation of abrupt current trajectories during the loss PLL phase. Active power compensation and dc current retention are achieved simultaneously. The theoretical analysis is verified through extensive simulations, whereas experimental validation is carried out on a scaled-down test bench.

This article introduces a compensation methodology that enables the coordination of multiple dc–dc converters to mitigate the second-order voltage harmonic component in hybrid microgrids. The proposed methodology utilizes metaheuristic algorithms to prohibit circulating currents and share harmonic currents among the compensating circuits. The proposed method can be easily implemented by any dc–dc converter while its efficacy is independent of the feeders’ impedances and the physical location of the compensating equipment. The elimination of circulating currents and the capability to share the total compensation current between the compensating circuits are not affected by the line impedances. In addition, the implementation of the proposed scheme does not require any expensive real-time communication. The mathematical analysis of hybrid microgrids seen from the perspective of harmonic compensation by coordinating multiple dc–dc converters is also presented, being a useful tool to design compensation methods. In addition, a qualitative and a quantitative comparison of the proposed methodology with prior-art methods in the literature are presented to further demonstrate the performance of the proposed solution. Finally, simulations and experimental tests verify the effectiveness of the proposed methodology.

During the last decade, microinverters have gained a considerable share in residential photovoltaic (PV) systems’ market. However, in order to be accepted by the marketplace, the reliability of microinverters must be comparable with that of traditional PV string and multistring inverters. A typical reliability issue that these systems experience, particularly in single-stage/single-phase topologies, is the presence of a large electrolytic capacitor for decoupling the power pulsation caused by the single-phase power generation. For this reason, several decoupling topologies have been introduced, which manage to decouple the power pulsation by using high reliability components, i.e., small capacitors (usually film ones) and power MOSFET transistors. Among these topologies, the family of bidirectional buck–boost-based parallel active filter (PAF) converters has been highlighted due to their minimum counterparts and their robust design. The main contribution of this paper is the unified theoretical analysis and the investigation of the operational limitations of this family of PAF converters, as well as the introduction of a control technique, which overcomes those restrictions. Simulation and experimental results validate the derived PAF family analysis and also prove the effectiveness of the introduced control technique.

In this work, a novel performance analysis method for evaluating the robustness of emerging power distribution networks (PDNs), which involve deployable renewable energy sources, is proposed. This is realized with the aid of the outage probability (OP) criterion in the context of cooperative communications, which is widely considered in modern wireless communication systems. The main usefulness of this method is that it allows the involved components to communicate to each-other by means of a robust and flexible wireless sensor network architecture. In this context, any conventional medium voltage (MV) bus of the PDN is represented as a wireless relay node where data signals gathered from each MV bus can be forwarded reliably to a control station for the subsequent processing. The received signals at wireless nodes are decoded and then forwarded to ensure minimal errors and maximal robustness at the receiving site. The considered OP analysis denotes the probability that the power of a received information signal drops below a pre-defined threshold which satisfies the acceptable Quality of Service requirements of a reliable signal reception. To this end, simple closed-form expressions are proposed for the OP of a regenerative cooperative-based PDN in the presence of various multipath fading effects, which degrade information signals during wireless transmission. The offered results are rather simple and provide meaningful insights for the design and deployment of smart grid systems.

We present an integrated approach for automating service providers’ compliance with data protection laws and regulations, business and technical requirements in cloud computing. The techniques we propose in particular include: natural language analysis (of legislative and regulatory texts, and corporate security rulebooks) and extraction of enforceable rules, use of sticky policies, automated policy enforcement and active monitoring of data, particularly in cloud environments. We currently work on developing a software tool for semantic annotation and natural language processing of cloud ToS and other related policy texts. We describe our implementations of two parts of the proposed toolkit, namely the semantic annotation editor and the EnCoRe policy enforcement framework. We also identify opportunities for future software development in the area of cloud computing compliance.

The field of cryptology and data security hardly needs any introduction; numerous popular accounts of the subject have appeared over the years, and it is already a core topic in undergraduate computer science. The very term "cryptology" is testimony to the long history of the field; the term is derived from the words κσνπτós (meaning hidden), and λóγos (meaning speech), which have retained their meaning in the Greek language for many centuries.