This work proposes a generic method to utilize customer smart meter measurements to automatically and simultaneously estimate topology, line parameters, and customer and line phasing connections in ...low voltage (LV) distribution systems. This generic approach is applicable to single, two, and three-phases lines and customers. Hence, it is suitable not only for North American systems but also for European and South American systems. This generic estimation is conducted by using a multiple linear regression model applied to data supplied by customers meters. The acceptance of each estimated parameter is carried out through comparisons with mathematical (e.g., coefficient of determination and relative standard deviation) and physical constraints (e.g., resistances, line length, and conductor X/R ratios). Granularity and sensitivity analyses are also conducted taking into account smart meter data quality (e.g., update ratio, metering errors, resolution, clock desynchronization). The obtained results show the high performance of the method to correctly estimate the system topology, line parameters, and line and customers phasing based on a specification of 15-day sample size with 60-min resolution as a general compromise solution between data acquisition and accuracy.
The smart meters installed at the customer premises are one of the main apparatuses promoting the modernization of the distribution systems. These devices collect a huge amount of data, demanding the ...development of analytic techniques to transform these data into useful information. In addition, by proposing new applications to data supplied by smart meters, more value is added to this equipment, allowing higher return on the associated investments. Utilities can have a business case by increasing their operational efficiency if smart meters are used, for instance, to identify non-technical losses, which represent an important cause of revenue losses. This paper presents a new data analytic technique for detection and location of non-technical losses caused by illegal connections of loads to distribution systems in the presence of smart meters. The data analytic technique relies on bad data analysis, similar to the ones used in state estimation methods, developed specifically for this application. A real 34-bus low voltage system is used to illustrate the main concepts of the proposed algorithm. Systematic tests are also conducted on a real 1682-bus distribution system to evaluate the method performance considering electricity theft caused by medium and low voltage customers.
•Practical method to determine whether shunt/series ESS can mitigate voltage sags.•Auxiliary chart obtained easily and analytically.•The method obtains Energy Storage System capacity required to ...mitigate voltage sags.•The method obtains the optimum power factor for operation of Energy Storage System.
Energy storage systems (ESS) have attracted significant interest and investments. Despite this interest, industry and utility engineers have not widely considered this technology as a potential solution to improve the power quality supplied for critical loads. This is in part because of the high cost and in part because of the high complexity to assess this type of solution. This paper, therefore, proposes a practical approach to determine whether shunt/series ESS can mitigate voltage sags assuming the availability of system information, as short-circuit impedance and historical voltage sags, and load information. This is done by analyzing a chart obtained analytically, which can be easily constructed based on simple information from the system and load, without resorting to computer simulations. By inspecting this chart, engineers can quickly determine not only the ESS capacity required to mitigate specific sags, but also which is the optimum power factor for operation. Sensitivity studies are provided to reveal key factors affecting ESS capability to mitigate voltage sags and to validate the proposed approach. Results outline that the requirements of shunt ESS depend on the system short-circuit level and X/R ratio, whereas requirements of series ESS depend on the load demand and power factor.
This article studies the Transmission Restoration Problem with Mobile Substation Resources, a novel mixed-integer linear programming model that prescribes the most effective usage of ...mobile-substation resources to enhance the resilience of a power transmission system against a particular, widespread flood event. The model is a two-stage stochastic program in which each scenario captures a different potential progression of flood heights at substations over the event horizon. The first stage concerns the pre-event selection and positioning of mobile-substation resources. The second stage concerns the coordination of mobile-substation resource deployment and permanent-substation restoration to maintain and recover service within the horizon. Experiments in the IEEE 24-Bus System and a synthetic Houston grid confirm the efficacy of the model. Even when isolated from effects related to restoration of permanent substations, the effect of four mobile transformers and eight mobile breakers for a realistic set of flood scenarios in the synthetic Houston grid was found to be an average total-cost reduction of approximately <inline-formula> <tex-math notation="LaTeX">{\} </tex-math></inline-formula>35MM (i.e., approximately 8% of a default optimal objective value). Additionally, a novel, parallel heuristic is designed that can efficiently solve the problem as well as, with minor modifications, similar stochastic problems on pre-selection of mobile resources or placement of static ones. For a 40-scenario model instance in the IEEE 24-Bus System, the extensive form was not able to find an integer-feasible solution in six hours, yet the heuristic achieved an optimality gap no worse than 4.5% in two hours.
The Pacific coastal desert of Peru harbors a unique bat fauna, including narrowly endemic taxa adapted to arid environments. This region was also the setting where several pre-Incan civilizations ...flourished. The Moche culture (100–850 CE) was one of those, with a rich and diverse material culture that included strikingly realistic ceramic representations of the regional flora and fauna. In particular, one Mochica pottery vessel is in the form of a bat that, based on external characteristics (large pinnae and tragus, pinnae connected by high band of membrane across the forehead, and lack of noseleaf), clearly represents an individual of the vespertilionid genus Histiotus. The morphological characteristics observed in this vessel, in addition to the area of influence of the Moche culture, suggests that this vessel depicts a species previously unknown to science that we describe here as new on the basis of two specimens obtained in 2012 in the Peruvian department of Piura. Our new species, Histiotus mochica, can be distinguished from other congeners by having unicolored dorsal fur, medial lobes of pinnae greater than 9.5 mm wide, and a well-developed (>4.3 mm high) transverse band of skin connecting the pinnae. Cytochrome b sequence data indicate that the new species is sister to H. humboldti from the Andes of Colombia and northern Ecuador. The new species is a medium-sized Histiotus that clusters with H. laephotis, H. velatus, and with small specimens of H. montanus in our multivariate analyses. With the description of H. mochica, the diversity of the genus increases to 11 species. We provide a key based on external characters of all known species of Histiotus.
Recent advances in inverter-based distributed energy resources (DERs) allow microgrids to operate in grid-connected and islanded modes with ease. However, determining a steady-state load flow ...solution of a real-world unbalanced and islanded three-phase microgrid remains a challenge. Existing methods are either unsuitable, labor-intensive or computationally demanding for a long-term analysis of islanded microgrids. To address these issues, we propose a practical solution framework that employs externally-updated system frequency, power quantities, and droop characteristics governing the voltage and phase angle of DERs in every iteration as inputs to an off-the-shelf open-source multi-phase, multi-wire, unbalanced power flow software tool to solve an islanded-microgrid power flow. Using our framework, users only need to implement a set of droop equations and update system variables. The power flow solution is accomplished entirely by an off-the-shelf power flow tool, e.g., OpenDSS. Our proposed framework can model a microgrid of any arbitrary configuration and operating condition. We demonstrate and validate the proposed method's efficacy by comparing its results with those modeled using a time-domain simulation with PSCAD/EMTDC. Finally, an example of a quasi-static time-series study is presented to better illustrate the application of such a tool.
This work proposes positive- and negative-sequence equivalent circuits of grid-forming inverters for steady-state analysis. The proposed models are especially attractive for performing long-duration ...voltage regulation analysis and short-circuit studies involving grid-forming inverters. Our proposed equivalent circuit models are based on the inverter's voltage and current control loops in the <inline-formula> <tex-math notation="LaTeX">\alpha \beta </tex-math></inline-formula> and dq frames. For this reason, they operate according to prescribed control functions and specified impedances ( i.e. , filter impedance, current limiter block, virtual admittance block, and PI/PR controller block). The equivalent circuit model accuracy is validated by comparing system steady-state voltage and current responses obtained by detailed time-domain models in PSCAD/EMTDC to those by the equivalent circuit models implemented in steady-state load flow program ( e.g. , OpenDSS). Two distinct control structures implemented in the <inline-formula> <tex-math notation="LaTeX">\alpha \beta </tex-math></inline-formula> and dq frames are used for the validation. Single line-to-ground and line-to-line-to-ground faults are simulated in a small islanded microgrid as well as the IEEE 34-node test feeder. Fault impedances varying from 0 to 5 ohms are simulated. We show that the equivalent models precisely replicate the steady-state response of the detailed time-domain models.
Millions of people worldwide are currently infected with human papillomavirus (HPV), herpes simplex virus (HSV) or human immunodeficiency virus (HIV). For this enormous contingent of people, the ...search for preventive and therapeutic immunological approaches represents a hope for the eradication of latent infection and/or virus-associated cancer. To date, attempts to develop vaccines against these viruses have been mainly based on a monovalent concept, in which one or more antigens of a virus are incorporated into a vaccine formulation. In the present report, we designed and tested an immunization strategy based on DNA vaccines that simultaneously encode antigens for HIV, HSV and HPV. With this purpose in mind, we tested two bicistronic DNA vaccines (pIRES I and pIRES II) that encode the HPV-16 oncoprotein E7 and the HIV protein p24 both genetically fused to the HSV-1 gD envelope protein. Mice i.m. immunized with the DNA vaccines mounted antigen-specific CD8⁺ T cell responses, including in vivo cytotoxic responses, against the three antigens. Under experimental conditions, the vaccines conferred protective immunity against challenges with a vaccinia virus expressing the HIV-derived protein Gag, an HSV-1 virus strain and implantation of tumor cells expressing the HPV-16 oncoproteins. Altogether, our results show that the concept of a trivalent HIV, HSV, and HPV vaccine capable to induce CD8⁺ T cell-dependent responses is feasible and may aid in the development of preventive and/or therapeutic approaches for the control of diseases associated with these viruses.
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