The design, construction and evaluation of a contactless battery charger for electric vehicles (EVs) based on inductive power transfer (IPT) is presented in this study. The design of such systems entails a high degree of complexity because of the large number of design parameters involved and, consequently, trade‐offs in selecting the key design parameters have to be established. The design process and selection of the IPT system parameters is detailed in this study, considering the most common specifications of EV chargers and the practical issues of the implementation. Regarding the compensation scheme, which is one of the main issues in the design, series compensation in both the primary and secondary has been adopted because of the advantages identified after a comprehensive analysis. A laboratory prototype has been built and tested, providing extensive results of the system performance in terms of efficiency and power transfer capability, considering load power variations, as well as changes in the air gap between coils. A detailed analysis of the efficiency of each stage in the IPT system and their contribution to the overall efficiency is also provided.

Outdoor IoT applications usually exploit energy harvesting systems to guarantee virtually uninterrupted operations. However, the use of energy harvesting poses issues concerning the optimization of the utility of the application while guaranteeing energy neutrality of the devices. In this context, we propose a new dynamic programming algorithm for the optimization of the scheduling of the tasks in IoT devices that harvest energy by means of a solar panel. We show that the problem is NP-Hard and that the algorithm finds the optimum solution in a pseudo-polynomial time. Furthermore, we show that the algorithm can be executed with a small overhead on three popular IoT platforms (namely TMote, Raspberry PI and Arduino) and, by simulation, we show the behavior of the algorithm with different settings and at different conditions of energy production.

The continuous monitoring of voltage characteristics in electric power systems, such as in microgrids, is required for power quality assessment, grid control, and protection purposes. Due to the presence of disturbances in the grid voltage, such as harmonics, imbalances, noise, and offsets introduced by the instrumentation, among others, the frequency-estimation process has to be robust against all these disturbances to obtain an accurate estimation of the frequency value. This paper presents a fast and accurate method to estimate the fundamental frequency of an electric power system. The estimation method works properly in balanced and imbalanced three-phase systems, and even in single-phase systems. The proposed solution is based on an algebraic method, which is able to calculate the frequency of a pure sinusoidal signal using three samples. A filtering stage is used to increase the robustness of the algorithm against disturbances in a wide frequency range. Simulation and experimental results show the good performance of the method for single- and three-phase systems with a high level of harmonic distortion, even in the presence of amplitude, phase, and frequency changes.

A new control strategy for induction motors based on direct torque control is presented which employs a three-level inverter instead of the standard two-level inverter. The controller is designed to achieve a torque ripple reduction by taking advantage of the increase in the number of inverter states available in a three-level inverter. The harmonic distortion in the stator currents and the switching frequency of the semiconductor devices are also reduced in the new control system presented.