Output Capacitance Minimization for Converters in DC Microgrids via Multi-Objective Tuning of Droop-Based Controllers

• Published in: IEEE access 2020, Vol.8, p.222700-222710
• Main Authors: Serrano-Delgado, Javier, Mattavelli, Paolo, Cobreces, Santiago, Abedini, Hossein, Rizo, Mario, Buso, Simone, Bueno, Emilio Jose
• Format: Article
• Language: English
• Subjects: Capacitance; Capacitance bridges; DC microgrids; DC-DC power conversion; Distributed generation; Electric bridges; Electric converters; Electric potential; H-infinity control; Impedance; impedance shaping; Microgrids; Minimization; multi-objective tuning; Optimization; Optimization techniques; Proposals; Tuning; Voltage; Voltage control; Voltage converters (DC to DC)
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2020.3044171

This paper proposes a controller tuning methodology for voltage-current droop-based DC-DC converters in DC microgrids to reduce the output capacitance. This minimization is cost saving and implies lower fault currents. However, it leads to higher DC voltage variability during load transients, which requires an output impedance shaping by control means to reduce over or undershoot. The proposed control structure and problem definition simultaneously takes into account that the solution must achieve the impedance shaping, performance and stand-alone stability objectives. This comprises a multi-objective problem which is effectively formulated here and, then, solved by a non-smooth \mathcal {H}_\infty optimization technique that tunes all free parameters. For comparison purposes, this tuning methodology is applied to several droop proposals, and the proposed droop is able to reduce the output capacitance of bidirectional buck-type and boost-type half-bridge converters by 37.5% and 23.08%, respectively, with respect to previous proposals. The designs are validated in time and frequency domains by means of theoretical analysis and experimental results on DC microgrid prototypes with bidirectional buck-type or boost-type half-bridge converters.