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Phasor measurement units (PMUs) provide synchronized measurements to enhance power system monitoring, strategically placed to achieve full network observability with minimal cost. In this paper, the PMU placement problem for critical buses is addressed using integer linear programming, taking into account both PMU contingencies and the impact of zero-injection buses. The primary contribution is the development of a multi-stage approach to place PMUs on critical buses. Moreover, it is demonstrated that considering PMU contingencies inherently accounts for line contingencies. Furthermore, a new performance metric, the Bus Coverage Index (BCI), is proposed to evaluate the effectiveness of the placement strategy. This index overcomes the limitations of existing indices, such as the Sum of Redundancy Index (SORI) and Bus Observability Index (BOI). The results are tested on various IEEE benchmark systems under four different cases, showing significantly improved results in terms of network observability and minimized number of PMUs. In Case 1, SORI values improved significantly for the IEEE 7 and IEEE 118 bus systems, while in Case 2, enhancements were observed in the IEEE 30 and IEEE 118 systems. Case 3 demonstrated consistency in results across systems. Notably, in Case 4, the number of required PMUs was reduced in the IEEE 30, IEEE 57, IEEE 118, and New England 39 bus systems, with complete network observability. [ABSTRACT FROM AUTHOR] more...

As the world's demand for sustainable and reliable energy source intensifies, the need for efficient energy storage systems has become increasingly critical to ensuring a reliable energy supply, especially given the intermittent nature of renewable sources. There exist several energy storage methods, and this paper reviews and addresses their growing requirements. In this paper, the energy storage options are subdivided according to their primary discipline, including electrical, mechanical, thermal, and chemical. Different possible options for energy storage under each discipline have been assessed and analyzed, and based on these options, a handsome discussion has been made analyzing these technologies in the hybrid mode for efficient and reliable operation, their advantages, and their limitations. Moreover, combinations of each storage element, hybrid energy storage systems (HESSs), are systems that combine the characteristics of different storage elements for fulfilling the gap between energy supply and demand. HESSs for different storage systems such as pumped hydro storage (PHS), battery bank (BB), compressed air energy storage (CAES), flywheel energy storage system (FESS), supercapacitor, superconducting magnetic coil, and hydrogen storage are reviewed to view the possibilities for hybrid storage that may help to make more stable energy systems in the future. This review of combinations of different storage elements is made based on the previous literature. Moreover, it is assessed that sodium-sulfur batteries, lithium-ion batteries, and advanced batteries are the most helpful element in HESSs, as they can be hybridized with different storage elements to fulfill electricity needs. The results also show that HESSs outperformed other storage systems and, hence, hybridizing the characteristics of different storage elements can be employed for optimizing the performance of energy storage systems. [ABSTRACT FROM AUTHOR] more...

The optimal PMU placement problem is placing the minimum number of PMUs in the network to ensure complete network observability. It is an NP-complete optimization problem. PMU placement based on cost and critical nodes is solved separately in the literature. This paper proposes a novel approach, a degree of centrality in the objective function, to combine the effect of both strategies to place PMUs in the power network optimally. The contingency analysis and the effect of zero-injection buses are solved to ensure the reliability of network monitoring and attain a minimum number of PMUs. Integer linear programming is used on the IEEE 7-bus, IEEE 14-bus, IEEE 30-bus, New England 39-bus, IEEE 57-bus, and IEEE 118-bus systems to solve this problem. The results are evaluated based on two performance measures: the bus observability index (BOI) and the sum of redundancy index (SORI). On comparison, it is found that the proposed methodology has significantly improved results, i.e., a reduced number of PMUs and increased network overall observability (SORI). This methodology is more practical for implementation as it focuses on critical nodes. Along with improvement in the results, the limitations of existing indices are also discussed for future work. [ABSTRACT FROM AUTHOR] more...

Multifunctional polymer matrix composites (PMCs) exhibiting increased thermal and electrical conductivity can be achieved by adding conductive carbon-based fillers in the polymer matrix. Emerging markets for thermally and electrically conductive PMCs include heat management devices in electronics, light emitting diodes, and/or photovoltaics cells as well as bipolar plates in fuel cells. In this study, the effects of micro-sized and nanosized carbon fillers [e.g., pitch-based carbon fibers (CF), multiwalled carbon nanotubes (MWNT), and graphene nanoplatelets (GNPs)] on the multifunctional properties of polyphenylene sulfide (PPS) matrix composites were investigated. Among the three carbon-based fillers, experimental results revealed that GNPs were the most effective fillers to promote the PMC's effective thermal conductivity ([k.sub.eff]). The highest ken of 1.94 W/m K was attained by adding 30.0 wt% (i.e., 22.4 vol%) of GNPs in the PPS matrix. The nano-sized MWNTs and GNPs had lower percolation threshold than the micron sized CFs to suppress the composite's electrical impedance. However, the coefficient of thermal expansion and the compressive elastic modulus of the composites were only slightly improved with the filler addition. The different levels of improvement in the composite's multifunctional properties can be related to the filler geometry, filler size, and the composite's phase morphology. POLYM. ENG. SCI., 53:2398-2406, 2013. © 2013 Society of Plastics Engineers, INTRODUCTION Engineering plastics are gaining traction in various emerging markets such as under-the-hood automotive applications, sensors and housing for motors, electronic components, and light-emitting diodes (LED), replacing traditionally used metal [...] more...

In the modern power systems, controllable loads are integrated through demand response (DR) programs and energy storage systems are exploited to provide virtual inertia (VI) with the help of power converters. The effectiveness of DR and VI in improving the power system's performance is well-addressed in the literature, however, their impact on the power system's stability is not well-documented. In this work, a novel analytical model is developed for sensitivity and stability analysis of power system frequency response with respect to important system parameters considering DR and VI. The developed model considers the individual and combined role of DR and VI control loops in the power system. The model is validated through extensive simulations on different systems with slow and fast dynamics. It is shown that, despite providing better frequency response, the introduction of DR and VI control loops can sometimes deteriorate the stability margins of the power system. The findings of this study call for careful calculations during the process of integrating DR and VI controls to the conventional power system. [ABSTRACT FROM AUTHOR] more...

With the recent developments in power electronics technologies, increased deployment of distributed energy resources (DER) with DC output type at distribution voltage levels and significant increase in the number of sensitive AC and DC loads integrated in distribution network have enforced the traditional power network in the continuous renovation process. In this paper, the load flow solution of hybrid AC/DC distribution networks with the multi-terminal configuration is studied. The impact of voltage source converter (VSC) losses and AC and DC line losses in the presence of DER in the distribution system are assessed. The motivation of this analysis is to consider an increase in the number of converter stations which might result in non-negligible converter losses and the presence of various DER within the network imposing different network scenarios. The proposed schemes are simulated on two modified IEEE 33 bus hybrid AC/DC distribution network test system equipped with VSC-MTDC and the results are presented. Obtained results show that by considering the network losses and the converter losses with large number of converters within the network could lead to very different load flow solution and power transfer between networks, especially considering the AC or DC bus dominated network. [ABSTRACT FROM AUTHOR] more...

The day-by-day increase in digital loads draws attention towards the need for an efficient and compatible distribution network. An LVDC distribution network has the capability to fulfill such digital load demands. However, the major challenge of an LVDC distribution network is its vulnerability during a fault. The need for a high-speed fault detection method is inevitable before it can be widely adopted. This paper proposes a new fault detection method which extracts the features of the current during a fault. The proposed fault detection method uses the merits of overcurrent, the first and second derivative of current, and signal processing techniques. Three different features are extracted from a time domain current signal through a sliding window. The extracted features are based upon the root squared zero, second, and fourth order moments. The features are then set with individual thresholds to discriminate low-, high-, and very high-resistance faults. Furthermore, a fault is located through the superimposed power flow. Moreover, this study proposes a new method based on the vector sum of positive and negative pole currents to identify the faulty pole. The proposed scheme is verified by using a modified IEEE 13 node distribution network, which is implemented in Matlab/Simulink. The simulation results confirm the effectiveness of the proposed fault detection and identification method. The simulation results also confirm that a fault having a resistance of 1 m Ω is detected and interrupted within 250 μ s for the test system used in this study. [ABSTRACT FROM AUTHOR] more...

A low voltage direct current (LVDC) distribution network is a promising technology to meet the standards of future energy demands for smart loads. An LVDC distribution network can not only supply efficient, smooth and clean energy, but also makes the integration of renewable energy resources in the distribution system easy. A major obstacle in the implementation of the LVDC distribution network is the protection of the network during abnormal grid conditions, such as transients and faults. This paper analyzes DC fault characteristics considering an LVDC distribution network, highlights the worst case scenario during a fault and protection related issues and proposes the protection schemes for the LVDC network. In the proposed protection scheme, a fault is detected and located through superimposed components. To minimize the effect of the DC fault on the distribution network, distributed fault current limiters are introduced and the final decision to disconnect or reconnect the affected line is made on the basis of the type of fault. In addition, a reclosing scheme for a temporary fault is proposed to avoid high inrush currents and false tripping, which eventually increases the reliability. A fast communication-based backup protection is also suggested, and to reduce dependency, a secondary backup is used in the case of communication delay or failure. The proposed scheme is verified using the modified IEEE 13 node test system, which is implemented in ATPDraw. The results show that the proposed scheme can successfully detect, locate and limit a DC fault in an LVDC distribution network with different fault resistances or locations. Moreover, the network is restored successfully in the case of temporary faults. [ABSTRACT FROM AUTHOR] more...

A correction to the article "A Load Flow Analysis for the AC/DC Hybrid Distribution Network Incorporated with Distributed Energy Resources for Different Grid Scenarios" by M.O. Khan is presented.

Background: Methicillin resistant Staphylococcus aureus (MRSA) is a common pathogen which has increased both morbidity and mortality in hospitals and out-door patients. Objective: Aim of our study is to measure prevalence of MRSA in in-door patients and outdoor patients, as well as its sensitivity against gentamycin, vancomycin and ciprofloxacin. Methods: A sample of 194 S. aureus was taken retrospectively from Pathology lab of a tertiary care hospital. MRSA was identified and further subjected against gentamycin, vancomycin and ciprofloxacin. Result: 65.9% of S. aureus isolates were MRSA. 22.7%, 35.7%, 99.1% of MRSA were susceptible to ciprofloxacin, gentamycin and vancomycin, respectively. 75.8% MRSA was from pus samples. 66% MRSA was from in-door patient department (IPD). Conclusion: MRSA was more prevalent in IPD. MRSA prevalence is escalating. Vancomycin is losing its effectiveness against MRSA as one resistant case was found. Inappropriate use and unprofessional prescriptions for antibiotics can be the main cause. Proper legislative action is required to keep in control the prescriptions for antibiotics. [ABSTRACT FROM AUTHOR] more...