The integration of renewable energy sources (RES), energy storage systems (ESS), and electric mobility into smart grids requires the use of dc-dc back-end power converters for adjusting voltage levels. Although a dc-dc converter applied for RES only operates in unidirectional mode, when applied to ESS or EM, the bidirectional mode is a fundamental requisite for exchanging power with the electrical power grid. In this context, this paper presents an experimental validation of a proposed bidirectional three-level dc-dc converter considering its application for smart grids. Traditionally, the dc-dc power converters of such applications are two-level converters. However, by employing a three-level topology, it is possible to improve the quality of the variables controlled by the power converter. Moreover, since the proposed dc-dc converter is controlled to produce a controlled current, the proposed current control and modulation strategies are introduced and described. A complete analysis of the operation principle of the proposed bidirectional three-level dc-dc power converter is presented, supported by experimental validation, employing a laboratory prototype.

This paper presents a three-phase three-level fast battery charger for electric vehicles (EVs) based in a current-source converter (CSC). Compared with the traditional voltage-source converters used for fast battery chargers, the CSC can be seen as a natural buck-type converter, i.e., the output voltage can assume a wide range of values, which varies between zero and the maximum instantaneous value of the power grid phase-to-phase voltage. Moreover, using the CSC it is not necessary to use a dc-dc back-end converter in the battery side, and it is also possible to control the grid current in order to obtain a sinusoidal waveform, and in phase with the power grid voltage (unitary power factor). Along the paper is described in detail the proposed CSC for EVs fast battery charging systems: the circuit topology, the power control theory, the current control strategy and the grid synchronization algorithm. Several simulation results of the EV fast battery charger operating with a maximum power of 50 kW are presented.

This paper presents a comparative analysis of power electronics topologies that can be used to interface dc homes with a 230 V, 50 Hz ac power grid. Dc homes represent an essential asset for smart grids, since energy storage systems and renewable energy sources, such as photovoltaic solar panels, operate in dc, as well as most of the electrical appliances used in domestic scenario. However, since the power grid operates in ac, it is necessary to convert voltage from ac to dc to properly supply a dc home. This conversion can be accomplished in several ways, with different power conversion stages. In this context, this paper analyzes three different possibilities that can be used to perform the interface between the ac power grid and a dc home: (1) ac-dc converter using a low frequency transformer; (2) ac-dc and dc-dc converters using a high frequency transformer; (3) ac-ac and ac-dc converters using a medium frequency transformer. These three possibilities are compared in terms of efficiency, total power factor and total harmonic distortion of the ac power grid. The results were obtained by means of a simulation model based on the internal parameters of the power semiconductors.

This paper describes different types of parallel association of Shunt Active Power Filters, presents computer simulation models developed in PSCAD®/EMTDC™, and shows simulated results for each case. The control system used in the active filters is based on the Instantaneous Reactive Power Theory (p-q Theory). The active filters use periodic sampling as switching technique. Two types of parallel associations are presented: two active filters in different parallel feeders; and both active filters connected in parallel at the same point of the electric installation. The paper also proposes a control strategy to solve an inherent operation problem that occurs in the second type of parallel association.

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