• Energy Research

Cyber security of distribution power systems is of an increasing and pressing importance due to the fast modernisation of current systems. Cyber attacks on distribution power systems may aim to operate the system inefficiently, steal private smart meter data or cause intentional false tripping of few or all feeders. In this paper, a Man in The Middle (MiTM) attack on a power factor correction unit is implemented and demonstrated to overload a distribution feeder and cause an intentional false tripping of the entire feeder causing regional blackout. Experimental implementation of the attack is carried out in a laboratory-scale setup using commercial power equipment under different loading conditions to demonstrate the effectiveness of this attack.

Harmonic distortions have adverse effects on the operation of the power system. Harmonic sources in low voltage distribution grids (LVDG) are highly dispersed in nature.Therefore, managing the resulting voltage and current distortions through conventional measures, such as passive or active power filters, becomes challenging. This work coordinates the harmonic injection capabilities of enhanced photovoltaic inverters to form a distributed active power filter. The proposed method aims to reduce the voltage and current distortions of the LVDG with fair utilization of inverters. Towards this direction, a lexicographic optimization scheme is formulated to derive the inverters’ harmonic current set-points by (i) minimizing the harmonic voltage limit violations, (ii) maximizing the inverter utilization fairness based on Jain’s fairness index, and (iii) minimizing the compensating currents of the inverters to reduce their lifetime degradation. The resulting optimization model is non-convex, thus a convex second-order cone program (SOCP) is formulated by relaxing the non-convex constraints and reformulating the Jain’s index as an SOCP constraint. Moreover, an iterative algorithm is developed to find the feasible operating point that maximizes the Jain’s fairness value. Simulation results indicate the superiority of the proposed scheme compared to existing methodologies in mitigating harmonic distortions in three-phase four-wire LVDGs.

System inertia directly affects the power system‘ s frequency response when an active power imbalance between generation and demand occurs. Therefore, determining the inertia level is becoming crucial to the system operators to ensure the secure and stable operation of a power system. This paper presents a method for estimating the total inertia of a generation bus considering only frequency and active power measurements recorded by Phasor Measurement Units (PMUs). The method allows online inertia monitoring utilizing ambient data, while a disturbance is not required to provide sufficient excitation to the system for accurate estimation. The Least Squares (LS) method is applied for parameter estimation to extract the inertia values from the identified models. Three different models have been studied to approximate the system's ambient response and extract the value of the inertia constant. The effectiveness of the proposed approach is demonstrated using actual measurements obtained from two substations of the Cyprus power system.

The forward/backward sweep is the most commonly used power flow method in radial Low Voltage Distribution Grids (LVDGs). In most cases, Kron's reduction is used to merge the neutral conductor with the phase conductors. However, important information can be lost by ignoring the effect of the neutral conductor through the Kron's reduction method, since in LVDGs the majority of loads are single-phase connected and are supplied through a phase conductor and the neutral. In this paper, a modification to the forward/backward sweep method is proposed to account for the neutral voltage as well. Test results indicate the significance of knowing the exact configuration of the neutral conductor in an LVDG before conducting power flow studies as it can affect greatly the accuracy of the results.

Las centrales eléctricas tienen un impacto negativo en el medio ambiente. Uno de estos impactos es la emisión de dióxido de carbono (CO2) resultante de las centrales eléctricas que dependen de combustibles fósiles, petróleo y gas natural. La energía renovable se considera una solución importante para este problema, ya que está clasificada como una fuente de energía limpia y respetuosa con el medio ambiente y ayuda a reducir la dependencia de las centrales eléctricas convencionales. La alta penetración de energía renovable en los sistemas de energía es un gran desafío que se puede resolver mediante el despliegue del concepto de micro-redes inteligentes. Este documento presenta un estudio sobre cuánta reducción de las emisiones de CO2 puede resultar del despliegue del concepto de microrred inteligente en un campus universitario, el campus de la Universidad Alemana de Jordania (GJU) se tomó como piloto. La microrred está diseñada para funcionar de acuerdo con un marco de programación de recursos óptimo que garantice un coste operativo mínimo y, al mismo tiempo, logre una alta disponibilidad de energía local. Les centrales électriques ont de mauvais impacts sur l'environnement. L'un de ces impacts est l'émission de dioxyde de carbone (CO2) résultant des centrales électriques qui dépendent des combustibles fossiles, du pétrole et du gaz naturel. L'énergie renouvelable est considérée comme une solution importante à ce problème car elle est classée comme une source d'énergie propre et respectueuse de l'environnement et contribue à réduire la dépendance aux centrales électriques conventionnelles. La pénétration élevée des énergies renouvelables dans les systèmes électriques est un grand défi qui peut être résolu en déployant le concept de micro-réseaux intelligents. Cet article présente une étude sur la réduction des émissions de CO2 pouvant résulter du déploiement du concept de micro-réseau intelligent sur un campus universitaire, le campus de l'Université germano-jordanienne (GJU) a été pris comme projet pilote. Le micro-réseau est destiné à fonctionner selon un cadre optimal de planification des ressources qui garantit un coût opérationnel minimum tout en assurant une disponibilité élevée de l'énergie locale. 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. 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 an important solution for this problem since it is classified as a clean and environmentally friendly source of energy and helps reduce 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 guarantees a minimum operational cost while achieving high local power availability. لمحطات الطاقة آثار سيئة على البيئة. أحد هذه التأثيرات هو انبعاثات ثاني أكسيد الكربون الناتجة عن محطات الطاقة التي تعتمد على الوقود الأحفوري والنفط والغاز الطبيعي. تعتبر الطاقة المتجددة حلاً مهمًا لهذه المشكلة لأنها تصنف كمصدر نظيف وصديق للبيئة للطاقة وتساعد على تقليل الاعتماد على محطات الطاقة التقليدية. يعد الاختراق العالي للطاقة المتجددة في أنظمة الطاقة تحديًا كبيرًا يمكن حله من خلال نشر مفهوم الشبكات الصغيرة الذكية. تقدم هذه الورقة دراسة حول مقدار الحد من انبعاثات ثاني أكسيد الكربون الذي يمكن أن ينتج عن نشر مفهوم الشبكة الصغيرة الذكية في حرم الجامعة، وقد تم أخذ حرم الجامعة الألمانية الأردنية (GJU) كبرنامج تجريبي. تهدف الشبكة الصغيرة إلى العمل وفقًا لإطار عمل جدولة الموارد الأمثل الذي يضمن الحد الأدنى من التكلفة التشغيلية مع تحقيق توفر طاقة محلية عالية.

This paper presents a Wide Area Control (WAC) method to coordinate the local controllers of generators and Renewable Energy Sources (RESs), for robust power oscillation damping. The WAC signals are synthesized by a two-level hierarchical controller, which utilizes wide area measurements from all the installed synchronous generators and RESs for maximizing the performance of their corresponding local controllers. In the resulting WAC scheme, the generators are “aware” of the RES oscillations and vice versa, the RESs are “aware” of the generator oscillations. Further, the WAC signals intended for the RESs are adjusted in order to require only slight modifications on the RES local controllers. This study illustrates that the correct coordination of generators and RESs, through the WAC, improves the damping performance of the entire system even under high penetration of renewables. The performance of the proposed scheme has been tested and validated in the IEEE 9-bus and 39-bus test systems. L. Zacharia, L. Hadjidemetriou and E. Kyriakides, "Integration of Renewables into the Wide Area Control Scheme for Damping Power Oscillations," in IEEE Transactions on Power Systems (Early Access). doi:10.1109/TPWRS.2018.2822315 © 2018 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.

The over-installation of renewable energy sources (RES) can enhance the profits of RES producers by increasing the total exporting energy; however, RES power curtailments must be applied under over-production of RES plants to ensure their contracted maximum export capacity limits. Battery energy storage systems (BESSs) can be used to reduce the RES curtailments and therefore enhance the profits of producers. This work develops a bidding strategy as a scenario-based stochastic optimization scheme to maximize the expected profits of producers in electricity markets considering battery degradation and maximum export capacity constraints. Using the proposed scheme, a financial analysis is performed to assess the profitability for over-installing hybrid RES plants by calculating the net present value and internal rate of return of the project under different BESS costs. Simulation results, using real data from a wind and photovoltaic plant, demonstrate the effectiveness of the proposed stochastic scheme in enhancing the profit of producers compared to the corresponding deterministic scheme. The performed financial analysis, using the net present value metric, indicates that a maximum over-installation of 150%–170% and 160%–180% for the wind and photovoltaic plant, respectively, is profitable, while the usage of a BESS is profitable when its cost is under 200,000 €/MWh.