• Energy Research

<p>This industry-oriented paper presents an overview and in-depth analysis of previous and current situations of power system frequency response and control in Australia. The evaluation of different services provided by different electricity market players under the supervision of the Australian Energy Market Operator (AEMO) as an independent system operator provides lessons and an understanding of the current operation status with its real challenges and opportunities from frequency stability and security perspectives. Based on the evaluation of the current situation and future national planning, a number of research gaps and industrial technical issues are identified, and some perspectives on future research directions are presented to help move the power system transformation toward almost 100% renewable and more secure energy systems.</p>

As renewable energy (RE) penetration has a continuously increasing trend, the protection of RE integrated power systems is a critical issue. Recently, power networks developed for grid integration of solar energy (SE) have been designed with the help of multi-tapped lines to integrate small- and medium-sized SE plants and simultaneously supplying power to the loads. These tapped lines create protection challenges. This paper introduces an algorithm for the recognition of faults in the grid to which a solar photovoltaic (PV) system is integrated. A fault index (FI) was introduced to identify faults. This FI was calculated by multiplying the Wigner distribution (WD) index and Alienation (ALN) index. The WD-index was based on the energy density of the current signal evaluated using Wigner distribution function. The ALN-index was evaluated using sample-based alienation coefficients of the current signal. The performance of the algorithm was validated for various scenarios with different fault types at various locations, different fault incident angles, fault impedances, sampling frequencies, hybrid line consisting of overhead (OH) line and underground (UG) cable sections, different types of transformer windings and the presence of noise. Two phase faults with and without the involvement of ground were differentiated using the ground fault index based on the zero sequence current. This study was performed on the IEEE-13 nodes test network to which a solar PV plant with a capacity of 1 MW was integrated. The performance of the algorithm was also tested on the western part of utility grid in the Rajasthan State in India where solar PV energy integration is high. The performance of the algorithm was effectively established by comparing it with the discrete Wavelet transform (DWT), Wavelet packet transform (WPT) and Stockwell transform-based methods.

Distribution transformers (DTs) are deemed as one of the major and high-priced equipment of electrical grids and their destruction negatively affects the stability and security of the network. The insulation status of the transformer depends on the hotspot and oil temperatures. Accordingly, controlling and, if possible, reduction of transformer oil temperature will improve the insulation status. In this paper, the effect of using nano-oil on oil temperature and loading capacity increment (LCI) of DTs has been studied via the electro-thermal resistance model (E-TRM). The studied nanofluids are two volumetric concentrations of multi-walled carbon nanotubes (MWCNTs) and three volumetric concentrations of diamond nanoparticles dispersed in pure mineral oil (MO). First, the numerical results gained from the E-TRM method are compared and verified with the experiential results of a 500 kVA DT. As well as, the effect of using MWCNT, diamond and proposed ONF nanoparticles in the heat transfer capacity of the transformer are investigated and compared. The results demonstrate that the highest temperature reduction in comparison with MO among the studied nanofluids is about 1 °C and for nanofluid ODI2. While the use of hypothetical ONF nanofluid reduces the oil temperature by 2.7 °C. Finally, the LCI of DTs caused by the use of nanofluids is investigated by the proposed novel equation. The use of nanofluids, especially the proposed ONF nanofluid, leads to the LCI up to 5%.

The paper proposes a technique for the on-line estimation of Thevenin equivalent (TE) which only needs the present phasor measurements. The technique is based on the wide-area measurements including voltage and current phasors of the system loads and synchronous generators, so that it can simultaneously estimate TE of the system seen from the interested buses. The technique has two main steps. In the first step, the conventional impedance matrix $\bar Z_{\rm bus}$ is modified to be suitable for TE estimation. In the second step, a correction coefficient based on the sensitivity theory calculated by using two consecutive phasor measurements is applied to correct the diagonal terms of the $\bar Z_{\rm bus}$ matrix. Simulation results carried on the IEEE 39-bus and 118-bus test systems show that the proposed technique can accurately estimate the TE for both generation and consumption buses under any load-increase scenario. The comparison scenarios verify the superiority of the proposed technique over others.

This article deals with the stochastic scheduling of a microgrid (MG) to balance the economical and resilience metrics. In the proposed model, the MG resilience indices are integrated into the economic criteria to ensure the resilience of MG operation alongside the main MG actors' profit/loss. The MG fragility index, recovery efficiency index, MG voltage index, and lost load index are considered in the proposed planning model. Further, to make the results more realistic, the uncertainties associated with energy price and wind production, alongside with planning of energy storage systems and electric vehicles parking lots are considered. To achieve a better solution for the security-constraint operation of MG, AC network equations are included in the system modeling. Finally, a large-scale MG based on the IEEE-33 bus testbed is utilized to evaluate the effectiveness of the proposed stochastic scheduling program.

In this paper, the significance of cross-tied link between the solar photovoltaic (PV) modules in an array during partial shading conditions (PSCs) is introduced. In order to conduct a detailed analysis, twenty numbers of 20W PV modules ( $4\times 5$ ) are arranged in a series-parallel (SP) configuration. The change in the pre-arranged SP configured PV array is implemented using a cross-link matrix switch between parallels based on shadow patterns. The switch matrix based modified PV array configuration is called Adaptive-cross-tied (A-CT) configuration. An embedded system based adaptive switch matrix (ASM) controller is developed to control the cross-linking connections between the PV modules under the PSCs to improve global maximum power. In addition, a performance analysis is carried out and compared all PV modules arranged in conventional SP and A-CT configurations. Moreover, realistic shadow test cases are under consideration to characterize current-voltage (I-V) and power-voltage (P-V) characteristics. The output power of the PV array decreases as well as the P-V curves show multiple power maxima points., such as the local maximum power point (LMPP) and the global maximum power point (GMPP). LMPP and GMPP locations, mismatch loss (ML), enhanced fill factor (FF), decreased power loss (PL) and performance ratio (PR) are indicators of performance during experimental and MATLAB/Simulink studies.

L'intégration de parcs éoliens à grande échelle crée une incertitude importante et des défis techniques remarquables pour les systèmes électriques en raison de leur intermittence. Une modélisation complète de la structure de dépendance à l'énergie éolienne est essentielle pour la gestion de l'incertitude dans le fonctionnement optimal des systèmes électriques modernes avec de nombreux parcs éoliens. Cet article présente un cadre d'optimisation robuste et ajustable efficace par lequel la structure de dépendance complexe des parcs éoliens peut être modélisée dans les problèmes de répartition de l'énergie et des réserves. Une modélisation efficace de la structure de dépendance et son intégration dans la génération de vent et la planification de l'expédition des réserves peuvent éviter les incidents de réduction du vent et de délestage. L'approche proposée utilise une copule de vigne canonique comme modèle statistique flexible et approprié pour considérer à la fois les distributions conjointes et conditionnelles de n'importe quel nombre de parcs éoliens. Les résultats de la modélisation de la structure de dépendance canonique suggérée basée sur la copule de la vigne sont ensuite utilisés comme entrées efficaces pour le problème de répartition de l'énergie et des réserves économiques robustes et ajustables présenté. L'approche suggérée est examinée sur le système IEEE 118-bus, et les résultats de simulation démontrent que la méthodologie proposée par une modélisation efficace de la structure de dépendance est efficace et montrent également l'effet du niveau de corrélation de l'énergie éolienne sur le coût total. La integración de parques eólicos a gran escala crea una incertidumbre significativa y desafíos técnicos notables para los sistemas de energía debido a su intermitencia. El modelado integral de la estructura de dependencia de la energía eólica es esencial para la gestión de la incertidumbre en el funcionamiento óptimo de los sistemas de energía modernos con muchos parques eólicos. Este documento presenta un marco de optimización robusto y ajustable eficiente mediante el cual se puede modelar la compleja estructura de dependencia de los parques eólicos en problemas de despacho de energía y reservas. El modelado eficiente de la estructura de dependencia y su incorporación en la generación eólica y la programación de despachos de reserva pueden evitar incidentes de reducción de viento y de desprendimiento de carga. El enfoque propuesto utiliza una cópula canónica de la vid como un modelo estadístico flexible y apropiado para considerar las distribuciones conjuntas y condicionales de cualquier número de parques eólicos. Los resultados del modelo de estructura de dependencia basado en cópula de vid canónica sugerido se utilizan como insumos eficientes para el problema de despacho de reserva y energía económica robusta ajustable presentado. El enfoque sugerido se examina en el sistema IEEE 118-bus, y los resultados de la simulación demuestran que la metodología propuesta mediante el modelado eficiente de la estructura de dependencia es efectiva y también muestra el efecto del nivel de correlación de la energía eólica en el costo total. The integration of large-scale wind farms creates significant uncertainty and remarkable technical challenges for power systems due to their intermittency. Comprehensive wind power dependence structure modeling is essential for uncertainty management in the optimal operation of modern power systems with many wind farms. This paper presents an efficient adjustable robust optimization framework by which the complex dependence structure of wind farms can be modeled in energy and reserve dispatch problems. Efficient dependence structure modeling and its incorporation in wind generation and reserve dispatch scheduling can avoid wind curtailment and load shedding incidents. The proposed approach utilizes a canonical vine copula as a flexible and appropriate statistical model to consider both the joint and conditional distributions of any number of wind farms. The results of the suggested canonical vine copula-based dependence structure modeling are then utilized as efficient inputs for the presented adjustable robust economic energy and reserve dispatch problem. The suggested approach is examined on the IEEE 118-bus system, and simulation results demonstrate that the proposed methodology by efficient dependence structure modeling is effective and also show the effect of the wind power correlation level on the total cost. يخلق تكامل مزارع الرياح واسعة النطاق حالة كبيرة من عدم اليقين وتحديات تقنية ملحوظة لأنظمة الطاقة بسبب تقطعها. تعد النمذجة الشاملة لهيكل الاعتماد على طاقة الرياح ضرورية لإدارة عدم اليقين في التشغيل الأمثل لأنظمة الطاقة الحديثة مع العديد من مزارع الرياح. تقدم هذه الورقة إطار تحسين قوي فعال قابل للتعديل يمكن من خلاله نمذجة هيكل الاعتماد المعقد لمزارع الرياح في مشاكل إرسال الطاقة والاحتياطيات. يمكن لنمذجة هيكل الاعتماد الفعال وإدماجه في توليد الرياح وجدولة إرسال الاحتياطيات تجنب حوادث تقليص الرياح وسفك الأحمال. يستخدم النهج المقترح حبة الكرمة الكنسية كنموذج إحصائي مرن ومناسب للنظر في كل من التوزيعات المشتركة والمشروطة لأي عدد من مزارع الرياح. ثم يتم استخدام نتائج نمذجة هيكل الاعتماد القائم على الكرمة الكنسية المقترحة كمدخلات فعالة لمشكلة الطاقة الاقتصادية القوية القابلة للتعديل وإرسال الاحتياطي. يتم فحص النهج المقترح على نظام IEEE 118 - bus، وتظهر نتائج المحاكاة أن المنهجية المقترحة من خلال نمذجة هيكل الاعتماد الفعال فعالة وتظهر أيضًا تأثير مستوى ارتباط طاقة الرياح على التكلفة الإجمالية.