Advanced microgrids : centralized control for coordination of heterogeneous converters

• Autor(a) principal: Lucas Savoi de Araújo
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Repositório Institucional da UFMG
• Texto Completo: http://hdl.handle.net/1843/49835; https://orcid.org/0000-0001-9463-6699
• topic: Centralized control; Distributed generation; Droop control; Microgrids; Smooth transition; Harmonics; Heterogeneous converters; Unbalance compensation; Engenharia elétrica; Conversores; Energia elétrica - Distribuição - Baixa tensão; Geração distribuída de energia elétrica

Environmental concerns concomitant with the steady growth of energy demand have triggered government guidelines and interventions encouraging renewable-based distributed generators in low-voltage grids. Advanced microgrid (MG) is a promising model for reaching the goal of 100% renewable grid. A complete advanced MG control strategy must steer the power flow in grid-connected mode, regulate voltage/frequency in islanded mode, and perform power sharing between distributed energy resources (DERs) in both modes. Centralized control approaches, such as the power-based control (PBC), are well-known for achieving these three targets. A serious disadvantage of centralized MG structure using PBC approach is the existence of a single central converter to form the islanded MG. Central converter is a single point of failure, which reduces the capability of the MG expansion, and it is an expensive element for implementation of MGs. Thus, the objective of this work is to develop an improved MG structure using PBC together with a droop-based power-loop in voltage-controlled mode (VCM) converters. This allows the MG to operate in both modes without a central converter. The developed strategy achieves grid power flow control, power sharing, unbalanced current compensation, voltage/frequency restoration and smooth transitioning between modes without critical islanding detection. Moreover, the new approach considers single- and three-phase DERs, controlled in VCM or current-controlled mode, and DERs with self-imposed limits, characterizing a heterogeneous MG. Heterogeneous MG is closer to real-world practical application where several sorts of multi-owners converters comprise a coordinated MG to achieve common goals. Theoretical, simulation and hardware-in-the-loop tests are conducted to: first, develop a control for VCM converters to avoid the necessity of central converter; second, develop a centralized control for advanced MGs that considers heterogeneous converters; and, finally, to develop a control approach for harmonics compensation when VCM converters are connected to distorted grids. Real-time hardware-in-the-loop setup is used as primary method for validating the proposed development under several operating conditions. Results support the conclusion that centralized control proves to be a remarkable solution for advanced MG issues.