1,720,962 research outputs found
A stability-oriented design method for virtual impedance loop in droop-controlled converters
Full text linkIn this paper, a novel strategy for virtual impedance design in droop-connected converters is analysed; the method is based on the stability analysis of equivalent system loops and aims at defining feasible operating regions of the converter depending on the control parameters. The effect of the tuning on the regulating performances of the system then has been tested in a simulation environment
Modified droop control for the optimal management of the battery systems in isolated microgrids
Full text linkMicrogrids are often made up with Hybrid Power Plants (HPPs), which include storage batteries. To enhance system efficiency, it is important to manage the batteries so as to avoid that one gets charged at other batteries' expense. To reduce costs and increase robustness, a Microgrid Controller that communicates with all the HPPs can be avoided and the droop control is often adopted for the HPPs' interface inverters. This paper proposes a method to change the droop coefficients so as to get the described target with no communication available between the HPPs. Theoretical analysis is validated through a simulation carried out on a study case
Parallel-Connected Photovoltaic Inverters: Zero Frequency Sequence Harmonic Analysis and Solution
No full textHigh-power photovoltaic (PV) plants are usually constituted of the connection of different PV subfields, each of them with its interface transformer. Different solutions have been studied to improve the efficiency of the whole generation system. In particular, transformerless configurations are the more attractive one from efficiency and costs point of view. This paper focuses on transformerless PV configurations characterised by the parallel connection of interface inverters. The problem of zero sequence current due to both the parallel connection and the presence of undesirable parasitic earth capacitances is considered and a solution, which consists of the synchronisation of pulse-width modulation triangular carrier, is proposed and theoretically analysed. The theoretical analysis has been validated through simulation and experimental result
Control loops design in a grid supporting mode inverter connected to a microgrid
Full text linkThis paper deals with some design aspects of the control loops in a droop-controlled VSI connected to other inverters of greater ratings or to a strong grid, which sets the frequency. The design of a damping resistor in series with the AC filter capacitor is discussed and the impact of strong feedback between the output current and the capacitor voltage is investigated. Moreover an analysis of the derivative droop coefficients is carried out through a simplified equivalent circuit
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
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