Development of an Integrated Battery Management System for Improving Power Quality in Microgrids.

The present dissertation concerns about the implementation of a novel configuration of an Integrated Active Filtering System (AFS), coupled with a Sodium Metal Halides Battery (SMHB), to improve Power Quality in Microgrids. This work is developed within the European H2020 project NETfficient, “Energy and Economic Efficiency for Today’s Smart Communities through Integrated Multi Storage Technologies", under grant agreement No 646463. The first chapter is dedicated to state of the art analysis of all technologies involved in the present work. In particular, Microgrid (MG) paradigm, active filters and the SMHB technology have been discussed in depth. The second and the third chapters show two case-studies related to Microgrids installed in the Renewable Energy Platform of Sardegna Ricerche in Macchiareddu, Sardinia. In these chapters, the technical-economic feasibility of a microgrid implementation has been analysed. Two different solar power generation configurations have been investigated (amorphous and concentrated photovoltaic generation). The next chapter regards the implementation of the control algorithm of the AFS. The proposed control algorithm is based on the identification of the instantaneous active power which allows the determination of the switching pattern sequence for properly controlling a Four-Leg Voltage Source Inverter (4L-VSI). The control system allows at the same time the definition of charging/discharging battery current values. The adopted 3D Space Vector Pulse Width Modulation (3D-SVPWM) has been described and the results of a simulation on Matlab-Simulink environment has been shown. In the fifth chapter, the Sodium Metal Halides Battery technology has been investigated deeply. In particular, the implementation of a novel Thévenin equivalent circuit model has been presented. A comparison between an improved model that considers the presence of iron reactions and one that does not consider it and the associated results have been shown. The sixth chapter is focused on the sizing criteria of an LC-filter aimed to decouple the AFS and the SMHB. The sizing procedure and the results in terms of decoupling capability have been shown. The next chapter analyses different Frequency Based energy Management (FBM) aimed to optimise the charging and discharging phases of a Hybrid Energy Storage System (HESS). Two algorithms have been compared, highlighting the advantages and disadvantages of the two different strategies. The algorithm has been tasted based on residual power data related to the island of Borkum, in Germany, place of the NETfficient project implementation. Finally, in the seventh chapter the implementation on FPGA of the control algorithm for the modulation of a 4L-VSI has been developed on LabVIEW environment and the first tests on the effective operation of the chosen modulation on a prototype inverter assembled in the laboratory, has been presented.