1,720,985 research outputs found
Transient voltage and frequency stability of an isolated microgrid based on energy storage systems
No full textMicrogrid (MG) based on energy storage systems to share the load between distributed generation plants in operation mode is the main issue in MG. Stability is an important component in energy management and planning of MG especially in duration of system's operation such as fault occurrence in system. In this article, frequency and voltage control based on active and reactive power control methods are analyzed. Studies demonstrate that MG stable operation in cases of proper use of control strategies is existing. MG system control due to stability improvement in islanding mode (autonomous mode) after fault occurrence at upstream network are been studying. MG system in this article included two distributed generation (DG) units. All of DG units and loads are connected in parallel at point of common coupling (PCC). In islanding mode, according to violence dependence of system's dynamic to local load changes and stability improvement after fault occurrence, design of controller algorithm is necessary. In this article, demonstrate that to frequency-load control, one of DG units is master and the other one is slave. Proposed controller based on energy storage system is design according to load uncertain. In final section of article, due to demonstrating the improvement and superior robustness of proposed controller to load dynamic, fault occurrence in system and controller capability in over demand supply and decrease short term produced power, frequency and voltage control by energy storage system cooperation that is one of novelty in this article, consider a comparison between classic and proposed controller. Proposed control strategy under two scenarios (load change and fault occurrence) has a good performance. Finally, propose controller superior robustness performance evaluated by MATLAB software
Designing a power control strategy in a microgrid using PID/fuzzy controller based on battery energy storage
No full textPower stability based on energy storage systems to share the load between distributed generations (DG) in island mode is the main issue in the microgrids (MGs). Stability is an important component in energy management and planning of MG. At the first part of this article, definitions and stability issues classification are presented. In this article, power control based on active power method is analyzed. MG system control due to stability improvement in islanding mode (autonomous mode) after fault occurrence at the upstream network are been studying. In this article, MG included two DG units. These DG units and loads are connected in parallel at the point of common coupling (PCC). In islanding mode, according to violence dependence of system's dynamic to local load changes and stability improvement after fault occurrence, the design of controller algorithm is necessary. In this article, demonstrated that to frequency-load control, one of DG units is master and the other one is slave. Proposed controller based on energy storage system is designed according to load uncertain. In the final section, due to demonstrating the improvement and superior robustness of proposed controller to load dynamic, fault occurrence in system and controller capability in over demand supply and decrease short term produced power, frequency and voltage control by energy storage system. Consider a comparison between classic and proposed controller. Proposed control strategy under two scenarios (load change and fault occurrence) has a good performance. Finally, propose controller superior robustness performance evaluated by MATLAB/Simulink
Elevator Regenerative Energy Applications with Ultracapacitor and Battery Energy Storage Systems in Complex Buildings
Full text linkDue to the dramatic growth of the global population, building multi-story buildings has become a necessity, which strongly requires the installation of an elevator regardless of the type of building being built. This study focuses on households, which are the second-largest electricity consumers after the transportation sector. In residential buildings, elevators impose huge electricity costs because they are used by many consumers. The novelty of this paper is implementing a Hybrid Energy Storage System (HESS), including an ultracapacitor Energy Storage (UCES) and a Battery Energy Storage (BES) system, in order to reduce the amount of power and energy consumed by elevators in residential buildings. The control strategy of this study includes two main parts. In the first stage, an indirect field-oriented control strategy is implemented to provide new features and flexibility to the system and take benefit of the regenerative energy received from the elevator’s motor. In the second stage, a novel control strategy is proposed to control the HESS efficiently. In this context, the HESS is only fed by regenerated power so the amount of energy stored in the UC can be used to reduce peak consumption. Meanwhile, the BES supplies common electrical loads in the building, e.g., washing machines, heating services (both boiler and heat pump), and lighting, which helps to achieve a nearly zero energy building
Current harmonic losses resulting from first and second generation LED lights replacement with sodium vapor lights in a LV feeder
No full textThe LED lamps require a DC current for proper functioning, thus, in order to supply this current, the diode bridge rectifiers in the internal circuit of these lamps are used. One of the problems in the old generation LEDs was the low power factor in these lamps. After development of electronic devices with soft switching, a new generation of LED lamps with high power factor has come into the commercial market. For power factor correction of LED lamps, the single-stage power factor correction circuits (PFC) are often used including a DC-DC boost converter with pulse width modulation and transformer. Despite the recent developments, the low power quality and harmonic current distortion of LED lamps is one of the basic challenges. Although a low power LED lamp doesn't have significant harmonic effects in distribution networks, however, the integration of LED lamps, especially in the lighting feeders, would increase the harmonic current distortion and reduce the power quality. Increase in the current harmonics will increase the ohmic losses along the Feeder conductors of the distribution network. In this article, there has been an attempt to examine the decreased harmonic power losses resulting from replacement of older generation (150Watt) 38 LED lights (without power factor correction circuit) and modern LED lights (with single-stage power factor correction circuit) with (160Watt) sodium vapor lamps in a lighting feeder on a street. The low voltage feeder and LED lights information has been taken from a real network. Results show that by installing LED street lights with power factor correction circuit (PFC), the harmonic losses along the network conductors are decreased by 11% compared to the sodium vapor lights. In contrast, the harmonic losses are increased by 57% with LED lights replacement without power factor correction (PFC)
EV charging station implementation in urban and non-urban areas: policies, challenges, and opportunities
No full textThe rapid demand for electric vehicles (EVs) is increasingly driving the creation of new charging infrastructure for more cars. The year 2023 has seen an unprecedented increase in EVs, also aided by the goal of reducing emissions with clear medium- and short-term targets. This paper proposes an analysis on EV charging station infrastructure in urban and non-urban areas. The policies, challenges and opportunities related to the EV charging stations (EVCSs) will be explored. Also, the integration of EVs with the grid and the new opportunities that are emerging related to charging station will be investigated
Electric Vehicles Charging Stations Sharing Model Control
No full textThe fast-growing electric car market inevitably requires the construction of new infrastructures for recharging vehicles. The design of new parking lots should be done by analyzing the expected profiles and the type of environment considered, in order to take full advantage of the technology and choose the charging modes that best suit that context. This article analyzes the different electric vehicle charging modes, the regulations that govern them and the possible types of parking. Subsequently, it is proposed a model of control and regulation of power flows that, depending on the type of parking and the types of charging stations, can manage up to four recharges simultaneously, without oversizing the infrastructure. This model, called Sharing Model Control (SMC), offers charging options that customers can select through an app interface; allowing them to choose the type of charging and its cost according to their needs. The main advantage of SMC is to allow the management of the same number of customers with a smaller installation of charging infrastructure, with all the economic benefits that come with it
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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