Superimposed AC Signal Frequency Droop Assisted Scheme for Decentralized Power Management of Grid-Forming Controlled DC MG Including Multiple PMSG-WTs, DSs, and BESS Units

Effective power management in DC microgrids (MGs) with both dispatchable and non-dispatchable energy sources is essential for enhancing reliability and optimizing performance. This paper presents an integrated control strategy for decentralized power management (PM) in a DC MG featuring PMSG-based wind turbines (WTs), droop-controlled dispatchable sources (DSs), and battery energy storage system (BESS). Inspired by frequency signaling methods used in AC microgrids, our approach introduces a corrective AC signal superimposed on the reference DC output voltages of the controllers. The frequency of this signal serves as a global coordination indicator, enabling the establishment of unified multi-part P/ω droop curves that facilitate effective PM across various sources while ensuring appropriate SOC management for BESS. Key findings include: (i) The drooping frequency of the AC signal relative to each source's DC output power defines unified droop curves for decentralized PM and SOC control; (ii) DC-DC converters operate as controlled voltage sources in grid-forming mode, allowing autonomous transitions between power and voltage regulation states; and (iii) All generation and storage units contribute to generating the AC signal frequency, ensuring robust performance even with resource loss. This innovative control strategy enhances power balance within the MG while enabling regulated charging and discharging of BESS, demonstrating significant potential for improving the operational efficiency of DC microgrids.