Andrés A. Nogueiras Meléndez

Model Predictive Control Applied to an Improved Five-Level Bidirectional Converter

This paper presents an improved five-level bidirectional converter (iFBC) controlled by finite control set model predictive control (FCS-MPC). This control strategy consists in using the discrete time nature of the iFBC to define its state in each sampling interval. Using FCS-MPC the switching frequency is not constant; however, it is suitable to follow the current reference with low total harmonic distortion (THD). The iFBC prototype that was specially developed for obtaining experimental results is described in detail along the paper, as well as its principle of operation, power theory, and current control strategy. The iFBC was experimentally validated connected to the power grid through a second-order LfCf passive filter operating as an active rectifier and as a grid tie inverter. For both operation modes, the experimental results confirm the good performance (in terms of efficiency, low current THD, and controlled output voltage) of the iFBC controlled by FCS-MPC.

Electric Vehicles On-Board Battery Charger for the Future Smart Grids

The recent and massive investments in Electric Vehicles (EVs) reveal a change of paradigm in the transports sector and the proliferation of EVs will contribute to an effective reduction in the emissions of greenhouse gases. Nevertheless, for the electrical power grids EVs will be extra loads, which will require the demand energy to charge their batteries. With the advent of the Smart Grids, besides the usual battery charging mode (Grid-to-Vehicle – G2V), where the batteries receives energy from the power grid, arises a new concept for the users of EVs and for the power grid market, denominated as Vehicle-to-Grid (V2G).In the V2G operation mode, EVs return to the power grid part of the energy stored in their batteries. The V2G concept requires the use of battery chargers for the EVs with bidirectional power flow capability and bidirectional communication with the Smart Grids through Information and Communication Technology (ICT) applications. It is important to highlight that the proliferation of EVs and the impact of their battery chargers on the power grid quality is a matter of concern, since conventional chargers present current harmonics and power factor problems. In this paper it is presented the preliminary studies resulting from a PhD work about a bidirectional battery charger for EVs, which was designed to operate in collaboration with the power grid as G2V and V2G through an ICT application. In this way, it is expectable to contribute to the technological innovation of the electric mobility in Smart Grids. To assess the behavior of the proposed battery charger under different scenarios of operation, a prototype has been developed, and some simulation and experimental results of the battery charger are presented.

On-board electric vehicle battery charger with enhanced V2H operation mode

This paper proposes an on-board Electric Vehicle (EV) battery charger with enhanced Vehicle-to-Home (V2H) operation mode. For such purpose was adapted an on-board bidirectional battery charger prototype to allow the Grid-to-Vehicle (G2V), Vehicle-to-Grid (V2G) and V2H operation modes. Along the paper are presented the hardware topology and the control algorithms of this battery charger. The idea underlying to this paper is the operation of the on-board bidirectional battery charger as an energy backup system when occurs a power outages. For detecting the power outage were compared two strategies, one based on the half-cycle rms calculation of the power grid voltage, and another in the determination of the rms value based in a Kalman filter. The experimental results were obtained considering the on-board EV battery charger under the G2V, V2G, and V2H operation modes. The results show that the power outage detection is faster using a Kalman filter, up to 90% than the other strategy. This also enables a faster transition between operation modes when a power outage occurs.

Geometric Analysis and Manufacturing Considerations for Optimizing the Characteristics of a Twisted Pair

The geometry of a twisted pair largely determines its electrical characteristics. To improve and refine the value of these characteristics according to preset values, the optimization of the manufacturing processes requires comprehensive knowledge of twisted pair geometry and of how electrical magnitudes are affected by the construction features of the twisted pair. This paper studies the relation between the length of a twisted pair cable and the length of each of the wires that compose the cable, by analyzing concepts such as pitch angle and radius of the helix. In addition, it examines the deformations and irregularities that can occur in the twisted pair during the manufacturing process and their effects on the geometry of the twisted pair. Results showed in this paper are a part of a larger research project carried out in association with the R&D department of a cable manufacturing company, and these results are being applied into the design department of this company.

Experimental validation of a proposed single-phase five-level active rectifier operating with model predictive current control

This paper presents a model predictive current control applied to a proposed single-phase five-level active rectifier (FLAR). This current control strategy uses the discrete-time nature of the active rectifier to define its state in each sampling interval. Although the switching frequency is not constant, this current control strategy allows to follow the reference with low total harmonic distortion (THDF). The implementation of the active rectifier that was used to obtain the experimental results is described in detail along the paper, presenting the circuit topology, the principle of operation, the power theory, and the current control strategy. The experimental results confirm the robustness and good performance (with low current THDF and controlled output voltage) of the proposed single-phase FLAR operating with model predictive current control.

Model predictive current control of a proposed single-switch three-level active rectifier applied to EV battery chargers

This paper presents a model predictive current control applied to a new topology of single-switch three-level (SSTL) active rectifier, which is exemplified in an application for single-phase battery charger for electric vehicles (EVs). During each sampling period, this current control scheme selects the state of the SSTL active rectifier to minimize the error between the grid current and its reference. Using this strategy it is possible to obtain sinusoidal grid current with low total harmonic distortion and unitary power factor, which is one of the main requirements for EVs chargers. The paper presents in detail the operating principle of the SSTL active rectifier, the digital control algorithm, and the EV battery charger incorporating the SSTL active rectifier used for the experimental verification. The obtained results confirm the correct application of the model predictive current control applied to the proposed SSTL active rectifier.

A B-learning new approach applied to a practical power electronics converters course

An Industrial Electronic discipline, involving different topics and technologies was designed to improve the sequence of activities within the available time and learning resources. The b-learning new methodology, applied in the University of Vigo, Spain, is composed of lectures, self-study sessions, quizzes, design problems, emulations, and laboratory sessions, integrated to achieve a better pedagogical environment. Most of the resources are available online without time restrictions, thus providing the students the opportunity to choose where and when they can learn, interact with the emulators, the remote laboratory and self-evaluate. Five flexible and powerful emulators have been developed for the buck, boost, buck-boost, forward and flyback converters. Emulation sessions provide a fast and easy path to understand the required concepts. The laboratory sessions are implemented by means of existing automatic test equipment (ATE), drive by a dedicated online server with new specific custom made software. The students provided positive evaluations of the methodology, and achieved a better degree of knowledge acquisition. Nowadays students from the University of Minho, Portugal, are also using remotely the set of resources available. The future work on this methodology will integrate the resources developed in both universities, to include more aspects of power electronics converters.

Three-phase current-source shunt active power filter with solar photovoltaic grid interface

This paper presents the proposal of a three-phase current-source shunt active power filter (CS-SAPF) with photovoltaic grid interface. The proposed system combines the compensation of reactive power and harmonics with the injection of energy from a solar photovoltaic array into the electrical power grid. The proposed equipment presents the advantage of giving good use to the current-source inverter, even when the solar photovoltaic array is not producing energy. The paper describes the control system of the CS-SAPF, the energy injection control strategy, and the current harmonics and power factor compensation strategy. Simulation results to assess the performance of the proposed system are also presented.

Simplified rail power conditioner based on a half-bridge indirect AC/DC/AC Modular Multilevel Converter and a V/V power transformer

This paper presents a comprehensive study about a Simplified Rail Power Conditioner (SRPC) based on a half-bridge indirect AC/DC/AC Modular Multilevel Converter (MMC) and a V/V traction power transformer. The proposed system with a half-bridge MMC can decrease the costs, reduce the control complexity, and require less hardware devices in comparison with the rail power conditioner based on a full-bridge indirect AC/DC/AC MMC. Moreover, the SRPC with a half-bridge MMC is able to compensate current harmonics, reactive power, and the Negative Sequence Components (NSCs) of currents, which are caused by the unbalance loads between power grid phases. This paper explains the system architecture and its control algorithms based on a pulse-width modulation and a proportional-integral controller, which is used to control the compensation currents. The simulation results of the SRPC show the submodule voltage balancing control and the DC-bus voltage control in order to verify its effectiveness. The compensation strategy based on the NSCs detection is described and evaluated through simulation results.

Experimental validation of a novel architecture based on a dual-stage converter for off-board fast battery chargers of electric vehicles

The experimental validation of a novel architecture of an off-board, three-phase fast battery charger for electric vehicles (EVs) with innovative operation modes is presented in this paper. The proposed EV fast battery charger is based on a dual-stage power converter (ac-dc and dc-dc) sharing the same dc link. The ac-dc stage is used as an interface between the power grid and the dc link. It is composed of the parallel association of two full-bridge voltage-source converters, and allows control of the grid current and of the dc-link voltage. The dc-dc stage is used as an interface between the dc link and the batteries. It is constituted by a bidirectional three-level asymmetrical voltage-source converter, and controls the flux of current during the EV battery charging process. Compared with the traditional solutions used for EV fast battery chargers, the proposed architecture operates as an interleaved converter, facilitating the reduction of the passive filters size, and the grid current harmonic distortion for the same switching frequency. Throughout the paper, the ac-dc and dc-dc stages, and the digital control algorithms are described in detail. The experimental validation was performed in a laboratory using a developed EV fast battery charger prototype, operating through the grid-to-vehicle and the proposed charger-to-grid modes, exchanging active, and reactive power with the power grid.