Cooperation of Wide Area Control with Renewable Energy Sources for Robust Power Oscillation Damping

In this paper, a Wide Area Control (WAC) scheme cooperates with Renewable Energy Sources (RESs) to achieve a robust power oscillation damping. The WAC signals are synthesized by a two-level hierarchical controller which utilizes global measurements from all the installed synchronous generators to maximize the performance of the generators’ local controllers. In the proposed WAC scheme, the dynamic operation of RES is also taken into consideration for the implementation of WAC signals, in order to make the generators “aware” of the RES oscillations. Further, the local controller of the RES is modified in order to utilize the available reactive power for compensating any local voltage oscillations, leading that way to a controller which does not require any WAC signals. The performance of the proposed scheme has been tested and validated in the IEEE 9-bus test system where it is indicated that the proposed scheme improves the power system’s dynamic stability

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Methods for Segmentation of Dental Data

72 σ.Η τμηματοποίηση κατέχει σημαντική θέση στην ιατρική απεικόνιση γιατί έχει ως στόχο την επιτυχή εξαγωγή χρήσιμων πληροφοριών από μια εικόνα και την χρήση τους για την δημιουργία πλάνου θεραπείας ή ακόμη και για καθοδήγηση σε χειρουργικές επεμβάσεις. Σκοπός της παρούσας διπλωματικής εργασίας είναι η παρουσίαση μιας ολοκληρωμένης μεθόδου τμηματοποίησης οδοντιατρικών δεδομένων, η οποία μπορεί να τμηματοποιεί επιτυχώς τα δεδομένα με την λιγότερη παρέμβαση του χρήστη. Κατά την δημιουργία της προτεινόμενης μεθόδου μελετήθηκαν διάφοροι αλγόριθμοι τμηματοποίησης όπως η ανίχνευση ακμών, η watershed κατάτμηση, η κατάτμηση με υφή και τα snakes. Από αυτούς έγινε κατάλληλος συνδιασμός της ανίχνευσης ακμής και του snake , για την δημιουργία του βέλτιστου αποτελέσματος που μπορεί να ληφθεί και βάση αυτών στηρλιχθηκε η υλοποίηση του τελικού αλγορίθμου.Segmentation plays an importan role in medical imaging because it aims for the successful extraction of useful informations from an image and their use to create treatment plan or even for surgical procedures. The purpose of this thesis is to present a complete method for segmentation of dental data, which can succesfully segment the data with as little user intervention. During the creation of the proposed method they have been studied various segmentation algorithms such as edge detection, watershed segmentation, texture segmentation and snakes. Amongst them it has been done an appropriate combination of the edge detection and the snake, to create the best result that can be obtained and based on them, has relied the creation of the final algorithm.Λάζαρος Χ. Ζαχαρί

Phase Balancing and Reactive Power Support Services for Microgrids

Alternating current (AC) microgrids are expected to operate as active components within smart distribution grids in the near future. The high penetration of intermittent renewable energy sources and the rapid electrification of the thermal and transportation sectors pose serious challenges that must be addressed by modern distribution system operators. Hence, new solutions should be developed to overcome these issues. Microgrids can be considered as a great candidate for the provision of ancillary services since they are more flexible to coordinate their distributed generation sources and their loads. This paper proposes a method for compensating microgrid power factor and loads asymmetries by utilizing advanced functionalities enabled by grid tied inverters of photovoltaics and energy storage systems. Further, a central controller has been developed for adaptively regulating the provision of both reactive power and phase balancing services according to the measured loading conditions at the microgrid’s point of common coupling. An experimental validation with a laboratory scale inverter and a real time hardware in the loop investigation demonstrates that the provision of such ancillary services by the microgrid can significantly improve the operation of distribution grids in terms of power quality, energy losses and utilization of available capacity

Design factors for developing a university campus microgrid

Recent decentralization of electricity systems together with the decarbonization and several changing societal demands are giving rise to different application scenarios such as microgrids. A microgrid is a small-scale electrical system which consists of several loads and sources (conventional and renewables) that can either operate autonomously in a stand-alone mode or interconnected with the main grid. The design and development of such a smart microgrid in a university campus is proposed within the 3DMicroGrid project (funded through the ERANETMED European Union\u27s initiative). This paper reviews the main components and characteristics of similar microgrids developed around the world. Furthermore, this study provides the design guidelines, the main functionalities, the key components and the control architecture for developing the microgrid proposed by the 3DMicroGrid project. A simulation model has been developed and initial results are demonstrated for the operation of this microgrid. The recommendations and insights are replicable to any solar priority country for future microgrids pilots

Hybrid multi-agent-based adaptive control scheme for AC microgrids with increased fault-tolerance needs

This paper presents a fault-tolerant secondary and adaptive primary microgrid control scheme using a hybrid multi-agent system (MAS), capable of operating either in a semi-centralised or distributed manner. The proposed scheme includes a droop-based primary level that considers the microgrid energy reserves in production and storage. The secondary level is responsible for: a) the microgrid units\u27 coordination, b) voltage and frequency restoration and c) calculation of the droop/ reversed-droop coefficients. The suggested architecture is arranged upon a group of dedicated asset agents that collect local measurements, take decisions independently and, collaborate in order to achieve more complex control objectives. Additionally, a supervising agent is added to fulfill secondary level objectives. The hybrid MAS can operate either with or without the supervising agent operational, manifesting fast redistribution of the supervising agent tasks. The proposed hybrid scheme is tested in simulation upon two separate physical microgrids using three scenarios. Additionally, a comparison with conventional control methodologies is performed in order to illustrate further the operation of a hybrid approach. Overall, results show that the proposed control framework exhibits unique characteristics regarding reconfigurability and fault-tolerance, while power quality and improved load sharing are ensured even in case of critical component failure

Microgrid Environmental Impact

Power plants have bad impacts on the environment. One of these impacts is Carbon Dioxide (CO2) emission resulted from power plants that depend on fossil fuel, oil and natural gas. Renewable energy is considered as an important solution for this problem since it is classified as clean and environmentally friendly source of energy and helps reducing the dependency on conventional power plants. High renewable energy penetration into power systems is a big challenge that can be solved by deploying the concept of smart Micro-Grids. This paper presents a study on how much reduction of CO2 emission can be resulted from deploying smart micro-grid concept on a university campus, German Jordanian University (GJU) campus was taken as a pilot. The micro-grid is meant to operate according to an optimum resource scheduling framework that guarantee a minimum operational cost while achieving high local power availability

Optimal Energy Management and Scheduling of a Microgrid in Grid-Connected and Islanded Modes

Microgrids are becoming one of the main components of future smart grids. Ensuring their optimal and stable operation is of crucial importance and can be a challenging task. In this paper, two optimization algorithms are implemented for scheduling the microgrid operation in grid-connected and islanded modes, according to the priorities and objectives in each mode. For achieving an optimal operation at each mode, the proposed scheme is able to shed loads, define the generation level of the photovoltaics and regulate the charging/discharging level of the Energy Storage System (ESS). The effectiveness of the proposed scheduling is demonstrated through an analytical real-time simulation, where various transitions between the grid-connected and islanded modes are considered. The results indicate that the proposed scheme is able to regulate successfully the energy flows of the microgrid even under various transitions