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SUMMARYThis paper presents a model of power light emitting diodes (LEDs) based on electrical variables and considering the concept of LED 'equivalent resistance', which has previously been used in discharge lamp modelling and is suitable to achieve fast simulations of LED converter systems. The model can be obtained with only some simple electrical measurements, thus making its implementation quite straightforward. The proposed model is oriented to the electronic engineering area, and it has special application for the simulation of the electrical behaviour of LEDs and dc-dc converter systems by using software like Simulink. In addition, the proposed model can also be employed for the theoretical analysis and design of LED drivers. Experimental and simulation results are obtained proving the feasibility of the proposed model.

A zero-ripple input current is known to improve the lifetime of battery sets and fuel cells and to assure maximum power point tracking in PV panels. To perform current ripple elimination in a floating interleaved boost converter (FIBC), one of the typical linear inductors is substituted by a variable inductor, and phases of the converter have complementary duty cycles. This variable inductor is controlled using a switched current-source converter, which adjusts the input current ripple. An equivalent model for the variable inductor is presented, including uncertainties in the component description. To achieve current stabilization, a variable inductor controller was designed using the sliding modes approach via fixed frequency. An experimental prototype is implemented and tested with an output voltage controller to compare with the conventional FIBC. The results demonstrate that the input current ripple of the proposed converter is eliminated without significantly decreasing the efficiency.

Renewable energy sources in DC microgrids require high-performance conversion systems to increase their capacity and reliability. Among other characteristics in conversion systems, the current ripple is a characteristic that must be considered since it affects the performance of PV panels and batteries. In this paper, a high-voltage-gain DC–DC boost converter for performing current ripple elimination that is based on a variable inductor is proposed. The topology is composed of a diode–capacitor voltage multiplier and a modified cascaded boost converter. To achieve voltage regulation, a reduced-order switched model is obtained considering the switched capacitor’s dynamics. To address the inductance variation and external disturbances, the H∞ control theory is adapted to systematically design a robust proportional–integral (PI) controller. Details of the working principles and the sizing of passive components are presented. The simulation and experimental results demonstrate that the input current ripple of the proposed converter can be removed in both transitory and steady states.

Photovoltaic systems are a technology for the generation of electrical energy that is constantly increasing thanks to current technological advances and that contributes to sustainable development. The main stages of photovoltaic systems are the conversion stage, using an inverter, and filtering. These systems may be considered as a mature and growing technology; however, regarding its reliability, there exists some uncertainties, and they are related to the operation, incidents, and its potential failures, due to the number of elements, the environment, and the operating nominal values. For this reason, this article presents a comparative analysis of the reliability of single-phase transformerless photovoltaic inverters used to inject active power into the grid. This evaluation is carried out under the same design specifications for all the inverters analyzed; the study is made using a mission profile considering the IEC TR 62380 standard, where the events and environmental operating conditions are defined, and numerical simulations. This work is aimed at providing suggestions to improve the quality of the photovoltaic system also considering reliability.

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