New approach of power calculation for droop-controlled inverters supplying nonlinear loads

Tesi en modalitat de compendi de publicacions (English) This thesis framework is that of the control of single-phase inverters in alternate current (AC) microgrids. In this context, voltage sourced inverters present difficulties in coping with power quality issues derived from highly distorted nonlinear loads. When these microgrids operate in islanded mode, the voltage sourced inverters control dynamic performance degrades in terms of stability and speed in attending to abrupt power demand changes. This is more noteworthy when the local control of the inverters follows the droop principles. In this case, nonlinear loads presence affects the dynamic performance of the specialized block utilized for calculating the necessary averaged active and reactive power references (P-Q). Even more, power-sharing among parallelized single-phase inverters needs an accurate P-Q calculation. Therefore, a fast and precise obtention of P-Q becomes essential for the stability of systems with droopoperated VSI. Following this motivation, research has been conducted towards the mitigation of the reported power quality issues. This work provided a novel approach for the P-Q calculation in the presence of single-phase nonlinear loads highly distorted in current. That resulted in a reduction in the transient time of the system's response against abrupt load changes and achieving more accurate P-Q quantities in steadystate. The novel approach was assessed and validated through Hardware in Loop and experimental tests in the Centre of Research on Microgrids of the University of Aalborg, and in the E3PACS laboratory facilities of EEBE-UPC. This work is organized as follows: in Section 1 are listed the objectives and in Section 2 contains an introduction and the state of the art. Section 3 sucinctly shows the main outcomes of this research through the published papers in JCR Q2 journals, in which the results were validated. Section 4 describes the methodology of the conducted research. Section 5 discusses the obtained results and Section 6 summaryzes the main contributions of this work, along with the general conclusions. Section 7 are listed future lines of work and Section 8 contain the mentioned references in this document. Finally, in Appendix I a description of a double (cascaded) second order general integrator is attached, followed with Appendix II and Appendix III where are listed all the published works related to the research, both JCR ranked journals and Conference Proceedin