Secondary Voltage Control for DC Microgrids: A Design Perspective for SoC With Voltage Restoration Provision

The energy management system (EMS) secondary voltage control design, integrating state-of-charge (SoC) equalization and droop control in redundancy-based dc microgrids (MGs), is ideal for vehicles, aircraft, and medical centers with sensitive loads. This paper proposes secondary voltage restoration in a dc MG to enhance S-shaped functions for SoC equalization among battery energy storage system (BESS) units. The dc MG topology is a cascaded bidirectional Cuk converter (CBC) linked to a cascaded bidirectional boost converter (CBB), both sharing two BESS units. The CBC is the primary module, while the CBB is an auxiliary module that operates under a failure in one of the Cuks, enhancing the dc MG resilience. Additionally, a fuel cell (FC) is connected to the CBC dc-link. The EMS for coordinating BESS and FC is modified by secondary voltage control to maintain the dc-link voltage at the set-point. Initially, the redundancy-based dc MG operates with voltage secondary control for the EMS, with infinity norm and Lyapunov's indirect method ensuring the stability analysis. Finally, the validation process is conducted integrating the SpeedGoat and dSPACE platforms.