The intermittent characteristics of microgrids (MGs) have motivated the development of energy management systems (EMSs) in order to optimize the use of distributed energy resources. In current studies, the implementation of an EMS followed by experimental-based analyses for both grid-tied and stand-alone MG operation modes is often neglected. Additionally, the design of a management strategy that is capable of preserving the storage device lifetime in battery-based MGs using a power gradient approach is hardly seen in the literature. In this context, this work presents the application of an EMS for battery-based MGs which is suitable for both grid-tied and stand-alone operation modes. The proposed EMS is formulated as an optimal power flow (OPF) problem using the-constraint method which is responsible for computing the current references used by the EMS to control the MG sources. In the optimization problem, the total generation cost is minimized such that the active power losses are kept within pre-established boundaries, and a battery management strategy based on power gradient limitation is included. Finally, the effectiveness of the proposed EMS is evaluated by two scenarios which enable detailed analyses and validation. The first considers a dispatchable and a non-dispatchable source, whereas the second a dispatchable source and a storage device. The experimental results showed that the proposed EMS is efficient in both operation modes and is also capable of smoothing the state of charge (SoC) behavior of the storage device. INDEX TERMS Battery power gradient, distributed generation, energy management system, microgrid, optimal power flow, storage device.
A B S T R A C TConsidering the relevant importance of guava (Psidium guajava) in Northeastern Brazil along with the benefits of neem cake amendments on soil characteristics, this work evaluated the effects of neem cake on chemical attributes of a Regosol under irrigated guava orchard in an alluvial valley of Pernambuco semi-arid region. Evaluations were carried out in two areas (area 1 -with neem cake; area 2 -without neem cake) at three periods: before the first application of neem cake, 90 days after the first application and 90 days after the second application. A regular 8 × 6-point grid was designed in each area and the soil was sampled for total organic carbon, pH, soluble salts (Na + , K + , Ca 2+ and Mg 2+ ) and total nitrogen contents, as well as soil C-CO 2 evolution rate in soil. Geostatistical analysis pointed out the spherical model as the best fit to the studied variables, followed by the Gaussian model, with ranges from 12 to 60.5 m. Neem cake incorporation increased spatial variability and the contents of the evaluated soil chemical attributes.Variabilidade espacial de atributos químicos em Neossolo no manejo da goiabeira com nim no semiárido R E S U M O Considerando a importância do cultivo de goiabeiras (Psidium guajava) para o nordeste do Brasil e os benefícios da aplicação da torta de nim nas características do solo, avaliou-se o efeito da aplicação de torta de nim nos atributos químicos de um Neossolo Regolítico cultivado com goiabeiras irrigadas no semiárido de Pernambuco. Para as avaliações foram usadas duas áreas (área 1 -com nim; área 2 -sem nim) e três períodos, antes da aplicação do nim, 90 dias após a primeira aplicação e 90 dias após a segunda aplicação; assim, 96 amostras de solo foram coletadas em duas malhas regulares de 8 × 6 pontos amostrais e realizadas análises do teor de carbono orgânico total, pH, teores de sais solúveis (Na + , K + , Ca 2+ e Mg 2+ ), nitrogênio total e taxa de evolução C-CO 2 do solo. O modelo esférico foi o que melhor se ajustou às variáveis estudadas seguido pelo gaussiano, com alcances que variaram de 12 a 60,5 m. A incorporação da torta de nim aumentou a variabilidade espacial e a oferta dos atributos de solo estudados.
Formerly in the literature, a new interleaved-based boost converter was devised for multiple input voltage sources purposes. Nevertheless, when only a single input voltage source is connected to the 2-phase version of this converter, it can be seen as a compact interleaved boost with voltage multiplier (cIBVM). A brief description of cIBVM operation as well as the ideal modeling are already discussed in the literature for one specific range of duty-cycle. In this paper, we provide further analysis by considering the conduction and dynamic losses on the analytical model with a single voltage source. Moreover, we also obtained the analytical model considering the entire duty-cycle range showing that the converter can perform either a quadratic, a double or even a symmetric voltage gain depending solely on the switching strategy adopted. The analytical model was obtained using state-space representation and both its accuracy and the effectiveness of the results were validated from a Simulink-based cross validation and a complete sequence of experimental tests. INDEX TERMS DC-DC converters, high step-up conversion ratio, multiple operation modes.
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