This paper presents the implementation of a single-controllable microgrid in the engineering school of the Federal University of Minas Gerais using commercial devices. Such a microgrid exchanges controllable active and reactive power terms with the upstream grid, proportionally shares active/reactive power among the battery-based DERs and endows the microgrid with the capability of operating in both grid-connected and islanded modes. The energy storage system is composed of three different battery technologies: lead-acid, lithium-ion and sodium–nickel, which are coordinately controlled according to their inherent features. A usable average energy control is proposed to avoid mismatches between the batteries’ states of charge. The single-controllable microgrid performs the following services: self-consumption, energy time shift, peak-shaving and reactive power support to the upstream grid. The coordinated secondary control and the operating modes of the microgrid were validated by means of full-scale experimental results using commercial devices. The lithium-ion battery showed the best performance in terms of round-trip efficiency, 93% over 85% (lead-acid) and 81% (sodium–nickel). The results demonstrated the microgrid’s capability of delivering ancillary services at the connection with the upstream grid, and proportionally exploiting the dispersed battery banks. In addition, the challenges of practical implementation were analyzed.

This paper proposes a modified version of the power-based control (MPBC) applied to microgrids (µGs) with multiple points of connection (i.e., utility grid itself or any other neighboring µG). Using the MPBC, single-phase distributed energy resources (DERs) arbitrarily connected between the phases share the amounts of balanced power, while the unbalanced and homopolar power are steered only to the line-to-neutral inverters. The control technique is based on a three-level hierarchical control using narrow bandwidth, low data rate communication that properly coordinates the DERs connected to three-phase four-wire µGs. The MPBC allows the DERs to steer power flow at any of the multiple points of common coupling of a multi-PCC dispatchable µG. The modified control proposed herein is evaluated through simulation results using MATLAB/SIMULINK considering a real urban distribution grid with typical operational elements and conditions. When compared to the original power-based control (PBC), results show that a meshed µG may reach power benchmarks with accommodation time 80% lower when applying MPBC. Moreover, it may also lead to significant power loss reduction (about of 5%) in some studied cases.

Over the years the world energetic matrix has modified. The clean generations with low carbon emissions are in the top of the attention. The worries about the environmental became the focus of electrical generation and it’s necessary generate energy as cleaner as possible. The photovoltaic energy is considered a clean energy, the energy conversion does not pollute the environment. Still little explored, it’s a technology considered expensive, because of it, is necessary find methods to reduce his cost benefits. Is this paper is evaluated the temperature influence in photovoltaic cells and a way to improve his efficiency through cooling. Ao longo dos anos a matriz energética mundial tem se modificado. As gerações limpas com baixas emissões de carbono vêm ganhando destaque. A preocupação com o meio ambiente, têm-se tornado foco das discussões na geração de energia, pois é necessário gerar energia elétrica de uma maneira mais limpa possível. A energia fotovoltaica se enquadra no contexto de geração limpa, pois a conversão de energia não polui o meio ambiente. Ainda pouco explorado, na grande maioria dos países, ela é uma tecnologia considerada cara, por conta disso é necessário encontrar métodos que diminuam seu custo benefício. Neste trabalho é avaliado a influência da temperatura na eficiência da célula fotovoltaica, e como aumentar a sua eficiência através do resfriamento.