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Publications

Publications by Luís Miguel Miranda

2016

Experimental validation of smart distribution grids: Development of a microgrid and electric mobility laboratory

Authors
Gouveia, C; Rua, D; Ribeiro, F; Miranda, L; Rodrigues, JM; Moreira, CL; Pecas Lopes, JAP;

Publication
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS

Abstract
The development of the Smart Grid concept is the pathway for assuring high reliability, control and management requirements in future electric power distribution systems. The Smart Grid can be defined as an electricity network supported by an intelligent infrastructure, both hardware and software, capable of accommodating high shares of Distributed Energy Resources. Within this line, a Smart Grid laboratorial infrastructure was developed, being dedicated to advanced research and demonstration activities. The adopted laboratorial architecture was developed according to the Microgrid concept, where Electric Vehicles are regarded as active and flexible players. Following the laboratory implementation, this paper provides a detailed description of its infrastructure and experimental capabilities, presenting and discussing different experimental set-ups and associated results.

2016

Voltage control demonstration for LV networks with controllable der - The SuSTAINABLE project approach

Authors
Costa, H; Miranda, M; Ramos, J; Seca, L; Madureira, A; Lemos, D; Santana, R; Louro, M; Matos, PG; Rosa, L; Silva, N;

Publication
IET Conference Publications

Abstract
One of the main constraints for Renewable Energy Sources (RES) integration in LV networks are overvoltages caused by changing the normal power flow of the network. In favourable weather conditions high voltages may lead to overvoltage trips thus preventing the injection of renewable energy into the grid. An optimized management of power injection from controlled RES to keep the grid voltage within regulatory limits enables a larger energy output and deployment of distributed generation. The SuSTAINABLE project developed a centralized algorithm based on a hierarchical methodology to control distributed power injection and solve the identified issue. A decentralized algorithm based on a coordinated droop control embedded in the inverters was developed as well. In order to evaluate the proposed algorithms a controllable PV µG and batteries were installed at the end of the feeder of a real LV network operated by EDP Distribuicao. The obtained results are presented in this paper and show that a hierarchical methodology to control power injection could optimize RES energy production while maintaining voltages within bounds, thus enabling a larger deployment of RES at the LV levels.

2017

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

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

Publication
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

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

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

Publication
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.

2016

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

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

Publication
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

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

Publication
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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