Growing demand, requirements for power quality enhancement and distribution generation are increasing the complexity of distribution systems. In this scenario, voltage regulation of distribution networks also becomes more complex, especially in long distribution lines. In this paper, a smart distribution transformer is proposed, which employs an electronic on load tap changer with a bidirectional communication system. This system enables automatic voltage regulation, telemetry and remote control for power utilities, allowing its application in Smart Grids.
Keywords -Electronic on load tap changer (OLTC), smart grids (SG), smart transformer (ST).
The aim of this paper is to create an education tool to estimate the losses and the dynamic behavior of the junction temperature of a semiconductor device, to be employed in a simulation software of electrical circuits. It must be highlighted that the temperature is one of the most important variables to be controlled in a switch-mode power converter and presents a great impact on converter efficiency and power density. Due to the lack of a simple tool to analyze the thermal behavior of a static converter, this paper proposes an algorithm to predict the losses (conduction and switching) and the temperature behavior in a semiconductor device. Using this algorithm the heatsink design can be optimized in order to project a converter with high power density. The methodology which easily extracts the loss and thermal models, without huge computational efforts, is demonstrated. The proposed approach can be used as an educational tool, since it can be easily implemented in a circuit simulation software, assisting students of Power Electronics. It is important to note, that experimental results are presented to validate the proposed approach.
With the aim of synthesizing high-fidelity voltage waveforms without penalizing the system efficiency, several works have proposed hybrid power amplifiers (HPAs), composed of linear and switching amplifiers, combining the benefits of each approach. According to the connection of the linear and the switched amplifiers, the HPAs are classified as envelope, parallel and series configurations. Each configuration holds particular characteristics that can be advantageous in some applications meanwhile to be quite stringent in others. This way, through a review of literature, this work aims to identify the features of each configuration, highlighting its benefits and possible limitations. The topologies proposed hitherto are analyzed from the circuit and control perspective. Therefore, this paper can be useful for one who is starting researching on this field or aims to select a suitable hybrid arrangement for a given application. Finally, an experimental case study is analyzed and future trends in research on HPAs are addressed.
Resumo-A crescente demanda por eletricidade, os requisitos de melhoria da qualidade de energia por parte dos agentes reguladores e a inclusão da geração distribuída estão aumentando a complexidade dos sistemas de distribuição. Neste cenário, a regulação da tensão torna-se mais complexa, especialmente em longas linhas de distribuição. Neste trabalho, um transformador de distribuição inteligente é proposto, o qual emprega um comutador eletrônico de taps sob carga, associado a um sistema de comunicação bidirecional. Este conjunto permite a regulação automática da tensão, telemetria e o controle remoto pela companhia concessionária, possibilitando sua aplicação nas redes de distribuição atuais e nas redes inteligentes, sendo caracterizado por sua fácil expansão.
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