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Publicações

Publicações por Diogo André Varajão

2017

Control of an isolated single-phase bidirectional AC-DC matrix converter for V2G applications

Autores
Varajao, D; Araujo, RE; Miranda, LM; Pecas Lopes, JP; Weise, ND;

Publicação
Electric Power Systems Research

Abstract
This paper describes a new current control method that enhances the dynamic performance of a single-phase bidirectional AC-DC battery charger to provide a high-frequency link between the grid and electric vehicle. The single-stage structure and the bidirectional power flow make the matrix converter an attractive solution for electric vehicle (EV) battery charging applications in the context of smart grids. The operating principles and modulation method are analyzed and discussed in detail. Furthermore, a current controller improved with a Smith predictor is proposed to decrease the phase delay in the measurement of the average current in the battery pack. The SP reduces the rise time to around a third and the settling time to half when compared with a PI controller. Simulations and experimental results from a laboratory prototype are shown to verify the feasibility of the proposed control scheme. © 2017 Elsevier B.V.

2013

Microgrid Service Restoration The Role of Plugged-In Electric Vehicles

Autores
Gouveia, C; Moreira, CL; Pecas Lopes, JAP; Varajao, D; Araujo, RE;

Publicação
IEEE INDUSTRIAL ELECTRONICS MAGAZINE

Abstract
The development of the microgrid (MG) concept endows distribution networks with increased reliability and resilience and offers an adequate management and control solution for massive deployment of microgeneration and electric vehicles (EVs). Within an MG, local generation can be exploited to launch a local restoration procedure following a blackout. EVs are flexible resources that can also be actively included in the restoration procedure, thus contributing to the improvement of MG operating conditions. The feasibility of MG service restoration, including the active participation of EVs, is demonstrated in this article through extensive numerical simulation and experimentation in a laboratorial setup. © 2007-2011 IEEE.

2013

Power flow control with bidirectional dual active bridge battery charger in low-voltage microgrids

Autores
Miranda, LM; Varajao, D; Dos Santos, B; Araujo, RE; Moreira, CL; Lopes, JAP;

Publicação
2013 15th European Conference on Power Electronics and Applications, EPE 2013

Abstract
This paper describes a power conversion system that implements bidirectional power flow between the electric grid and a battery, based on a full bridge inverter associated with a dual active bridge. A method for power flow control based on the agreement between battery pack and low voltage grid requirements has been developed to allow the large penetration of both, electric vehicles (EV) and renewable microgeneration. A laboratory prototype containing all functions required to implement a vehicle-to-grid (V2G) power interface has been built. The hardware implementation is reported, including control scheme and high-frequency transformer design details. Converter key waveforms are presented to evaluate the power quality on batteries and grid, as well as its dynamic behavior. An experimental laboratory setup is described and results are shown to demonstrate the technical benefits for low-voltage (LV) microgrids, if electric vehicle charger includes a power flow control based on frequency-voltage droop concept. © 2013 IEEE.

2013

Rapid Prototyping Framework for Real-Time Control of Power Electronic Converters Using Simulink

Autores
dos Santos, B; Araujo, RE; Varajao, D; Pinto, C;

Publicação
39TH ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY (IECON 2013)

Abstract
This paper presents a Rapid P rototyping Framework (RPF) based on MATLAB/Simulink and the next steps towards developing an interactive control architecture based on the TI TMS320F28335 DSP. Firstly, the rapid proto typing framework is described comprising the details of the tools and hardware. Secondly, the experiments towards the realization of a real-time control application for the experimental setup are revealed. Finally, a controller for managing the DC link control of EVs with multiple energy sources was implemented by the RPF to demonstrate the performance of the developed system.

2016

Power Transformer for a Single-stage Bidirectional and Isolated AC-DC Matrix Converter for Energy Storage Systems

Autores
Varajao, D; Miranda, LM; Araujo, RE; Pecas Lopes, JP;

Publicação
PROCEEDINGS OF THE IECON 2016 - 42ND ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY

Abstract
This paper presents an approach to design the transformer and the link inductor for the high-frequency link matrix converter. The proposed method aims to systematize the design process of the HF-link using analytic and software tools. The models for the characterization of the core and winding losses have been reviewed. Considerations about the practical implementation and construction of the magnetic devices are also provided. The software receives the inputs from the mathematical analysis and runs the optimization to find the best design. A 10 kW / 20 kHz transformer plus a link inductor are designed using this strategy achieving a combined efficiency of 99.32%.

2014

Towards a new technological solution for Community Energy Storage

Autores
Varajao, D; Miranda, LM; Araujo, RE;

Publicação
2014 16TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'14-ECCE EUROPE)

Abstract
Energy storage in low voltage grid is receiving increased attention due to renewables integration and consumption growth, challenges faced nowadays by grid operators. In this work, a study of main implementation issues for community energy storage (CES) is presented along with a comparison between possible solutions for the bidirectional isolated power conversion system (PCS) to interface a battery pack with the electric power grid. The aim of this research is to increase the power density of the power converter and keeping simultaneously the same reliability of traditional solutions. These goals are pursued to be achieved through the reduction of the conversion stages and utilization of new optimization methodologies to reduce the volume of the passive components. The proposed topology for the PCS is based on a matrix converter (MC) that performs a direct AC to AC conversion between the grid and a high-frequency transformer (HFT). With this solution it is possible to eliminate the traditional DC-link capacitor and obtain a single-stage power conversion with bidirectional power flow capability. This proposed solution is evaluated and compared with a conventional two-stage topology through extensive simulation. Two prototypes systems were designed for a 10kW PCS to connect the three-phase 230/400Vrms, 50Hz mains to a battery pack with voltage range of 320V to 490V. Simulation results are presented to assess the power quality provided by the front-end and the battery side converters, as well as performance evaluation and efficiency analysis.

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