Abstract The insertion of new distributed energy resources, such as distributed generation (DG), energy storage systems (ESS), demand response (DR), and microgrids (MG), is emerging, bringing new challenges to the current distribution network. In this regard, the active distribution networks (I) with multi-microgrids concept appears. The present paper proposes a hierarchical (master-slave problem) computational model to achieve optimal coordinated operation of multi-microgrids connected to an I. Day-ahead operation planning of an I was formulated as a multiperiod non-linear optimal power flow model, resulting in a non-linear optimization problem, additionally, the day-ahead operation planning of MGs was formulated as a multiperiod linearized optimal power flow resulting in a mixed-integer linear optimization problem. Numerical results on four different test-system microgrids connected to a 359-nodes ADNs test-system belonging to a Brazilian distribution company show the effectiveness of the proposed model and solution strategy. Three cases have been tested: with a maximum load-shedding restriction, without this restriction, and considering insertion of DG. Besides, the hierarchical model can evaluate how much losses and load shedding take effect without integrated operation and expansion planning of emerging distributed networks. This study showed the importance of analyzing the systemic impact of integrating multi-MGs and I synergistic operation interactions, resulting in improvements in the voltage quality levels, operation costs, and power losses. The results showed that, including DG in the system, the costs were reduced by 13,48% compared to the case base.

Abstract Distribution power grids are continuously changing, mainly due to the insertion of distributed energy resources. Since the late 90's the distribution generation insertion has been growing, changing the planning and operation of the conventional grid. More recently, storage systems are also being placed on the distribution power system, aiming to improve system power quality and reliability. In this context of active grids, an Optimum Power Flow (OPF) was proposed, integrating generation from distributed generation with photovoltaic systems as well as a battery energy storage, which could be located at different feeder busses, including the substation bus. The OPF was modeled in a multiperiod structure, allowing simultaneous evaluation of all steps within the time horizon, being solved with the interior points method implemented in python. Different scenarios were evaluated considering different distributed generation levels, as well as battery placement at the substation bus and in the middle of the grid. From the multiperiod OPF results, it is obtained the minimization of losses and operational costs of the system, besides the minimum battery cost and the optimum behavior of charge and discharge of the battery.

Abstract Microgrids (MGs) have increasingly attracted the attention of researchers, government officials, and electricity companies for the values and services they can add to the grid. They can operate independently as a single controllable unit in a coordinated way while connected or islanded, which make them suitable to integrate the growing amount of distributed energy resources (DERs) into the distribution network (DN). An active distribution network with high penetration of DERs could be redefined into a collection of microgrids in different layers, pooling their resources together to enhance the grid’s performance in the sense of electricity as a service. However, enabling a microgrid-based power system infrastructure poses challenges concerning operation and control. In this paper, a comprehensive overview of research topics regarding microgrid operation are shown in a hierarchical or stratified manner, looking for a holistic vision of a microgrid-based distribution system. First, multi-objective optimization within one microgrid is formulated aiming to minimize costs and maximize battery life is presented. Second, the interaction among MGs, DERs and the DN was modeled using the OPF technique to represent the operation of the grid as a whole. Following, a methodology for collaborative optimization of multiple MGs operating together is presented and at last a theoretical framework for MG operation through decentralized energy markets is discussed. As a result, this paper aims to contribute to a broad vision of the distribution system based on microgrid operation in all its levels.

Objetivo:revisar os prontuários de 19 pacientes com diagnóstico de amioplasia, submetidos à osteotomia extensora percutânea de fêmur distal, para correção de deformidade fixa em flexão dos joelhos.Métodos:analisamos 37 osteotomias em 35 joelhos com média de deformidade fixa inicial média em flexão dos joelhos de 33,8°, todos submetidos à osteotomia percutânea extensora do fêmur distal e acompanhados em média de 73,7 meses.Resultados:observamos recidiva da deformidade em 29 osteotomias, ou seja, 78,4% delas. A velocidade média de recidiva da deformidade foi de 0,69°/mês.Conclusão:a osteotomia extensora percutânea do fêmur distal forneceu correção suficiente da deformidade fixa em flexão dos joelhos na amioplasia, porém apresentou significativo grau de recidiva nos pacientes analisados.

Objective:to review the medical files of 19 patients with a diagnosis of amyoplasia, who underwent percutaneous extensor osteotomy of the distal femur to correct deformities in whom the knees were fixed in flexion.Methods:we analyzed 37 osteotomy procedures on 35 knees that presented an initial deformity in which the knees were fixed in flexion at 33.8°. All of these knees underwent percutaneous extensor osteotomy of the distal femur and were followed up for a mean period of 73.7 months.Results:we observed recurrence of the deformity in 29 osteotomy cases, i.e. in 78.4% of them. The mean recurrence velocity of the deformity was 0.69°/month.Conclusion:percutaneous extensor osteotomy of the distal femur provided sufficient correction of deformities in which the knee was fixed in flexion in these amyoplasia cases, but there was a significant degree of recurrence among the patients analyzed.