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Summary Dc microgrids are feasible and effective solutions for integrating renewable energy resources to the power system. However, the operation around an equilibrium point depends on the control strategy adopted for each operation mode. When operating in off‐grid mode, droop and maximum power point control are basic strategies employed to regulate the voltage across the dc link considering the lack of communication between the sources. In this context, this work describes some important issues regarding the application of such approaches in microgrids, where active and nonlinear loads such as constant‐power loads and constant‐impedance loads exist. In this case, the power sources are considered as a set of parallel‐connected current sources associated with their respective equivalent resistances. The proposed approximate model allows performing a nonlinear analysis to predict the qualitative behavior of the system due to the reduced number of differential equations. In addition, this analysis provides sufficient conditions to determine the operating points of the system, thus providing reliable design guidelines for the implementation of microgrids.

This paper describes the implementation of a Quadratic Boost-Buck converter (Boost2-Buck), with one active switch, used to drive a LED string for Photodynamic Therapy (PDT) purposes. The proposed converter can be powered from 12 V DC to 180 V DC (127 V AC). So it can be fed by battery or by utility power grid. Experimental results taken from a 80 W prototype are presented.

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Este artigo apresenta o projeto e implementação de um conversor Boost-Buck Quadrático (Boost-Buck2), com uma única chave ativa, utilizado no acionamento de um vetor de LEDs empregado em iluminação. O conversor proposto possui uma faixa larga de conversão de tensão o que torna possível ser alimentado de 12 V CC a 340 V CC (240 V CA). Esta característica permite que o conversor proposto seja aplicado em instalações elétricas híbridas alimentadas por sistemas fotovoltaicos e pela rede de energia elétrica de 110 V ou 220 V. Resultados experimentais extraídos de um protótipo de 11 W também são apresentados. Palavras-Chave-Conversor CC-CC, faixa larga de conversão, sistemas fotovoltaicos e vetor de LEDs.